<?xml version="1.0" encoding="UTF-8"?>

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2025 Workiva-->
<!--r:64bff10d-2ed5-4d24-b9a8-45e55c91ad1c,g:eba0e000-047d-40a9-bd4e-eb2fac35d790-->
<link:linkbase xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd">
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/all" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#all"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#hypercube-dimension"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-default"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-domain"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#domain-member"/>
  <link:roleRef roleURI="http://soterahealth.com/role/ConsolidatedStatementsofOperationsandComprehensiveIncomeLoss" xlink:type="simple" xlink:href="shc-20250630.xsd#ConsolidatedStatementsofOperationsandComprehensiveIncomeLoss"/>
  <link:definitionLink xlink:role="http://soterahealth.com/role/ConsolidatedStatementsofOperationsandComprehensiveIncomeLoss" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_4c779786-b3d8-4e8d-a206-75ce56a94c81" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_8db2b16d-b84d-4e1b-b93a-54ac3a85e91b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_4c779786-b3d8-4e8d-a206-75ce56a94c81" xlink:to="loc_us-gaap_StatementTable_8db2b16d-b84d-4e1b-b93a-54ac3a85e91b" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_99f29bc9-d003-44a5-93b0-691b8937f176" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_8db2b16d-b84d-4e1b-b93a-54ac3a85e91b" xlink:to="loc_srt_ProductOrServiceAxis_99f29bc9-d003-44a5-93b0-691b8937f176" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_99f29bc9-d003-44a5-93b0-691b8937f176_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_99f29bc9-d003-44a5-93b0-691b8937f176" xlink:to="loc_srt_ProductsAndServicesDomain_99f29bc9-d003-44a5-93b0-691b8937f176_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_e95fb9ea-b867-485a-89fc-3f3f4e9e4e6c" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_99f29bc9-d003-44a5-93b0-691b8937f176" xlink:to="loc_srt_ProductsAndServicesDomain_e95fb9ea-b867-485a-89fc-3f3f4e9e4e6c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ServiceMember_4857ae13-b976-4496-8d3b-1781f2765b8e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ServiceMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_e95fb9ea-b867-485a-89fc-3f3f4e9e4e6c" xlink:to="loc_us-gaap_ServiceMember_4857ae13-b976-4496-8d3b-1781f2765b8e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProductMember_ef80a61d-ee8c-4b54-aa55-0a990e74db37" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProductMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_e95fb9ea-b867-485a-89fc-3f3f4e9e4e6c" xlink:to="loc_us-gaap_ProductMember_ef80a61d-ee8c-4b54-aa55-0a990e74db37" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_LitigationCaseAxis_21684716-3e8f-4272-acb5-8cc314347830" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_LitigationCaseAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_8db2b16d-b84d-4e1b-b93a-54ac3a85e91b" xlink:to="loc_srt_LitigationCaseAxis_21684716-3e8f-4272-acb5-8cc314347830" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_LitigationCaseTypeDomain_21684716-3e8f-4272-acb5-8cc314347830_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_LitigationCaseTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_LitigationCaseAxis_21684716-3e8f-4272-acb5-8cc314347830" xlink:to="loc_srt_LitigationCaseTypeDomain_21684716-3e8f-4272-acb5-8cc314347830_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_LitigationCaseTypeDomain_e9521ace-e4fa-40ef-9688-5a883aa35b09" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_LitigationCaseTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_LitigationCaseAxis_21684716-3e8f-4272-acb5-8cc314347830" xlink:to="loc_srt_LitigationCaseTypeDomain_e9521ace-e4fa-40ef-9688-5a883aa35b09" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_EthyleneOxideTortLitigationIllinoisMember_b8727e57-c745-47dd-a3a9-43debdad4765" xlink:href="shc-20250630.xsd#shc_EthyleneOxideTortLitigationIllinoisMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_LitigationCaseTypeDomain_e9521ace-e4fa-40ef-9688-5a883aa35b09" xlink:to="loc_shc_EthyleneOxideTortLitigationIllinoisMember_b8727e57-c745-47dd-a3a9-43debdad4765" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenuesAbstract_bd54d947-0f64-4ab5-8bbd-d6628c37287d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenuesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_4c779786-b3d8-4e8d-a206-75ce56a94c81" xlink:to="loc_us-gaap_RevenuesAbstract_bd54d947-0f64-4ab5-8bbd-d6628c37287d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_e35a5da4-affe-438a-902b-4cc4a0e8a35e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenuesAbstract_bd54d947-0f64-4ab5-8bbd-d6628c37287d" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_e35a5da4-affe-438a-902b-4cc4a0e8a35e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostOfRevenueAbstract_a34309b0-d493-413c-b743-ccd6f1d1be5e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CostOfRevenueAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_4c779786-b3d8-4e8d-a206-75ce56a94c81" xlink:to="loc_us-gaap_CostOfRevenueAbstract_a34309b0-d493-413c-b743-ccd6f1d1be5e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostOfRevenue_26659d75-269c-46ec-8702-d2f90c1558b9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CostOfRevenue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostOfRevenueAbstract_a34309b0-d493-413c-b743-ccd6f1d1be5e" xlink:to="loc_us-gaap_CostOfRevenue_26659d75-269c-46ec-8702-d2f90c1558b9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GrossProfit_35d3b7f5-38d2-416b-a21e-eea20b650364" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GrossProfit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_4c779786-b3d8-4e8d-a206-75ce56a94c81" xlink:to="loc_us-gaap_GrossProfit_35d3b7f5-38d2-416b-a21e-eea20b650364" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SellingGeneralAndAdministrativeExpense_a86fc8ad-1b75-4b77-80fb-87f22e4965ec" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SellingGeneralAndAdministrativeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_4c779786-b3d8-4e8d-a206-75ce56a94c81" xlink:to="loc_us-gaap_SellingGeneralAndAdministrativeExpense_a86fc8ad-1b75-4b77-80fb-87f22e4965ec" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_AmortizationOfIntangibleAssetsNonproduction_a068743f-8dcd-405d-aade-79ba117c734e" xlink:href="shc-20250630.xsd#shc_AmortizationOfIntangibleAssetsNonproduction"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_4c779786-b3d8-4e8d-a206-75ce56a94c81" xlink:to="loc_shc_AmortizationOfIntangibleAssetsNonproduction_a068743f-8dcd-405d-aade-79ba117c734e" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainLossRelatedToLitigationSettlement_6dad644d-8f0c-486a-b8fd-eaffbfd037a1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GainLossRelatedToLitigationSettlement"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_4c779786-b3d8-4e8d-a206-75ce56a94c81" xlink:to="loc_us-gaap_GainLossRelatedToLitigationSettlement_6dad644d-8f0c-486a-b8fd-eaffbfd037a1" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestIncomeExpenseNonoperatingNet_f113ef10-3371-4e6d-a1e2-3e8642556908" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestIncomeExpenseNonoperatingNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_4c779786-b3d8-4e8d-a206-75ce56a94c81" xlink:to="loc_us-gaap_InterestIncomeExpenseNonoperatingNet_f113ef10-3371-4e6d-a1e2-3e8642556908" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_GainLossOnRefinancingOfDebt_22cf8c10-c3a8-4ca6-92c1-f0554e8406ec" xlink:href="shc-20250630.xsd#shc_GainLossOnRefinancingOfDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_4c779786-b3d8-4e8d-a206-75ce56a94c81" xlink:to="loc_shc_GainLossOnRefinancingOfDebt_22cf8c10-c3a8-4ca6-92c1-f0554e8406ec" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignCurrencyTransactionGainLossBeforeTax_a2370e39-ee4e-42b5-9ff4-614864565f59" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ForeignCurrencyTransactionGainLossBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_4c779786-b3d8-4e8d-a206-75ce56a94c81" xlink:to="loc_us-gaap_ForeignCurrencyTransactionGainLossBeforeTax_a2370e39-ee4e-42b5-9ff4-614864565f59" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherNonoperatingIncomeExpense_0d0a8385-f5a2-4375-87a0-68565049132f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherNonoperatingIncomeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_4c779786-b3d8-4e8d-a206-75ce56a94c81" xlink:to="loc_us-gaap_OtherNonoperatingIncomeExpense_0d0a8385-f5a2-4375-87a0-68565049132f" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_eef15195-8638-4519-b91f-eece37e36ee8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_4c779786-b3d8-4e8d-a206-75ce56a94c81" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_eef15195-8638-4519-b91f-eece37e36ee8" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxExpenseBenefit_c18b823e-4e79-41b7-8017-69ed31646dc4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxExpenseBenefit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_4c779786-b3d8-4e8d-a206-75ce56a94c81" xlink:to="loc_us-gaap_IncomeTaxExpenseBenefit_c18b823e-4e79-41b7-8017-69ed31646dc4" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_ebdf2175-761e-4fd2-bdea-4523a83f0750" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_4c779786-b3d8-4e8d-a206-75ce56a94c81" xlink:to="loc_us-gaap_NetIncomeLoss_ebdf2175-761e-4fd2-bdea-4523a83f0750" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParentAbstract_0e6df1d4-4e59-4335-af7b-431bcb44522f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParentAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_4c779786-b3d8-4e8d-a206-75ce56a94c81" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParentAbstract_0e6df1d4-4e59-4335-af7b-431bcb44522f" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax_92e90203-1264-4b4d-8391-4810ed4cb158" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParentAbstract_0e6df1d4-4e59-4335-af7b-431bcb44522f" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax_92e90203-1264-4b4d-8391-4810ed4cb158" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTax_1e367433-6324-40e0-bd07-576b644e3439" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParentAbstract_0e6df1d4-4e59-4335-af7b-431bcb44522f" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTax_1e367433-6324-40e0-bd07-576b644e3439" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax_74c59f15-06c2-4997-8057-cf52a9d2203c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParentAbstract_0e6df1d4-4e59-4335-af7b-431bcb44522f" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax_74c59f15-06c2-4997-8057-cf52a9d2203c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest_8d5b3a85-66e2-4543-bf69-a2782e5bd8dd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_4c779786-b3d8-4e8d-a206-75ce56a94c81" xlink:to="loc_us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest_8d5b3a85-66e2-4543-bf69-a2782e5bd8dd" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareAbstract_90d7ce0e-da66-43fb-b1dc-4b9277630d5c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EarningsPerShareAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_4c779786-b3d8-4e8d-a206-75ce56a94c81" xlink:to="loc_us-gaap_EarningsPerShareAbstract_90d7ce0e-da66-43fb-b1dc-4b9277630d5c" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareBasic_9b044add-7667-4d71-bdef-cb29b544de31" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EarningsPerShareBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareAbstract_90d7ce0e-da66-43fb-b1dc-4b9277630d5c" xlink:to="loc_us-gaap_EarningsPerShareBasic_9b044add-7667-4d71-bdef-cb29b544de31" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareDiluted_563e8686-5692-4773-bf75-90bd49085613" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EarningsPerShareDiluted"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareAbstract_90d7ce0e-da66-43fb-b1dc-4b9277630d5c" xlink:to="loc_us-gaap_EarningsPerShareDiluted_563e8686-5692-4773-bf75-90bd49085613" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_WeightedAverageNumberOfSharesOutstanding1Abstract_a1fec63a-11c7-4b44-be16-276d5c00b557" xlink:href="shc-20250630.xsd#shc_WeightedAverageNumberOfSharesOutstanding1Abstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_4c779786-b3d8-4e8d-a206-75ce56a94c81" xlink:to="loc_shc_WeightedAverageNumberOfSharesOutstanding1Abstract_a1fec63a-11c7-4b44-be16-276d5c00b557" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_8be2802a-a10d-41e2-ad75-849163f2bb51" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_shc_WeightedAverageNumberOfSharesOutstanding1Abstract_a1fec63a-11c7-4b44-be16-276d5c00b557" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_8be2802a-a10d-41e2-ad75-849163f2bb51" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_13e5d4ef-534b-42da-a189-ca0fe7b355c5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_shc_WeightedAverageNumberOfSharesOutstanding1Abstract_a1fec63a-11c7-4b44-be16-276d5c00b557" xlink:to="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_13e5d4ef-534b-42da-a189-ca0fe7b355c5" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://soterahealth.com/role/ConsolidatedStatementsofCashFlows" xlink:type="simple" xlink:href="shc-20250630.xsd#ConsolidatedStatementsofCashFlows"/>
  <link:definitionLink xlink:role="http://soterahealth.com/role/ConsolidatedStatementsofCashFlows" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_b2e950cf-6cb0-4839-be60-b5005cf330d3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_5dc1c5fa-fc7e-4b2b-b633-7f4f0e87f2ae" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_b2e950cf-6cb0-4839-be60-b5005cf330d3" xlink:to="loc_us-gaap_StatementTable_5dc1c5fa-fc7e-4b2b-b633-7f4f0e87f2ae" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_LitigationCaseAxis_c51b1d51-c4f1-437c-80c0-2d4d6c0bad0c" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_LitigationCaseAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_5dc1c5fa-fc7e-4b2b-b633-7f4f0e87f2ae" xlink:to="loc_srt_LitigationCaseAxis_c51b1d51-c4f1-437c-80c0-2d4d6c0bad0c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_LitigationCaseTypeDomain_c51b1d51-c4f1-437c-80c0-2d4d6c0bad0c_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_LitigationCaseTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_LitigationCaseAxis_c51b1d51-c4f1-437c-80c0-2d4d6c0bad0c" xlink:to="loc_srt_LitigationCaseTypeDomain_c51b1d51-c4f1-437c-80c0-2d4d6c0bad0c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_LitigationCaseTypeDomain_88864c14-b074-4629-90c9-8a9d759034e6" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_LitigationCaseTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_LitigationCaseAxis_c51b1d51-c4f1-437c-80c0-2d4d6c0bad0c" xlink:to="loc_srt_LitigationCaseTypeDomain_88864c14-b074-4629-90c9-8a9d759034e6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_EthyleneOxideTortLitigationIllinoisMember_20a78cb0-ea53-44e2-8576-017d5b8eab3e" xlink:href="shc-20250630.xsd#shc_EthyleneOxideTortLitigationIllinoisMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_LitigationCaseTypeDomain_88864c14-b074-4629-90c9-8a9d759034e6" xlink:to="loc_shc_EthyleneOxideTortLitigationIllinoisMember_20a78cb0-ea53-44e2-8576-017d5b8eab3e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_EthyleneOxideTortLitigationGeorgiaMember_ea502333-8a7b-4d0a-8e06-f823e864434d" xlink:href="shc-20250630.xsd#shc_EthyleneOxideTortLitigationGeorgiaMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_LitigationCaseTypeDomain_88864c14-b074-4629-90c9-8a9d759034e6" xlink:to="loc_shc_EthyleneOxideTortLitigationGeorgiaMember_ea502333-8a7b-4d0a-8e06-f823e864434d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_77484741-345e-463f-b6ef-dea8846c3ecc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_b2e950cf-6cb0-4839-be60-b5005cf330d3" xlink:to="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_77484741-345e-463f-b6ef-dea8846c3ecc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_45acdd15-09f1-4aed-b25f-4aecd73b0a4f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_77484741-345e-463f-b6ef-dea8846c3ecc" xlink:to="loc_us-gaap_NetIncomeLoss_45acdd15-09f1-4aed-b25f-4aecd73b0a4f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_0d75c686-c08e-4b35-ba0c-69c902e029aa" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_77484741-345e-463f-b6ef-dea8846c3ecc" xlink:to="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_0d75c686-c08e-4b35-ba0c-69c902e029aa" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Depreciation_cfc7d2f5-bf87-4109-a040-cc522326d3ed" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_Depreciation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_0d75c686-c08e-4b35-ba0c-69c902e029aa" xlink:to="loc_us-gaap_Depreciation_cfc7d2f5-bf87-4109-a040-cc522326d3ed" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AmortizationOfIntangibleAssets_27426d5e-b735-42e2-81f9-9449e690b55c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AmortizationOfIntangibleAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_0d75c686-c08e-4b35-ba0c-69c902e029aa" xlink:to="loc_us-gaap_AmortizationOfIntangibleAssets_27426d5e-b735-42e2-81f9-9449e690b55c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_GainLossOnRefinancingOfDebt_ec9bd1d0-7633-41a6-a1b7-9340afb37dc3" xlink:href="shc-20250630.xsd#shc_GainLossOnRefinancingOfDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_0d75c686-c08e-4b35-ba0c-69c902e029aa" xlink:to="loc_shc_GainLossOnRefinancingOfDebt_ec9bd1d0-7633-41a6-a1b7-9340afb37dc3" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredIncomeTaxExpenseBenefit_b2b5c222-7671-452f-a80d-844ed747c3de" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DeferredIncomeTaxExpenseBenefit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_0d75c686-c08e-4b35-ba0c-69c902e029aa" xlink:to="loc_us-gaap_DeferredIncomeTaxExpenseBenefit_b2b5c222-7671-452f-a80d-844ed747c3de" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensation_cf9dbab6-6fdf-49cc-a4ab-5156a6bced96" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_0d75c686-c08e-4b35-ba0c-69c902e029aa" xlink:to="loc_us-gaap_ShareBasedCompensation_cf9dbab6-6fdf-49cc-a4ab-5156a6bced96" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetRetirementObligationAccretionExpense_bca2d5cf-5b3a-4ea5-ac47-5007f1b592e1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AssetRetirementObligationAccretionExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_0d75c686-c08e-4b35-ba0c-69c902e029aa" xlink:to="loc_us-gaap_AssetRetirementObligationAccretionExpense_bca2d5cf-5b3a-4ea5-ac47-5007f1b592e1" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignCurrencyTransactionGainLossUnrealized_b04af0b1-442e-4a4b-be1a-c93632617921" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ForeignCurrencyTransactionGainLossUnrealized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_0d75c686-c08e-4b35-ba0c-69c902e029aa" xlink:to="loc_us-gaap_ForeignCurrencyTransactionGainLossUnrealized_b04af0b1-442e-4a4b-be1a-c93632617921" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnrealizedGainLossOnDerivatives_2f49dc97-78ea-48a2-9a1f-fdb05ea7b35a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_UnrealizedGainLossOnDerivatives"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_0d75c686-c08e-4b35-ba0c-69c902e029aa" xlink:to="loc_us-gaap_UnrealizedGainLossOnDerivatives_2f49dc97-78ea-48a2-9a1f-fdb05ea7b35a" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AmortizationOfFinancingCosts_0a3284b3-7fc1-4355-a7d8-c1d8107f478a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AmortizationOfFinancingCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_0d75c686-c08e-4b35-ba0c-69c902e029aa" xlink:to="loc_us-gaap_AmortizationOfFinancingCosts_0a3284b3-7fc1-4355-a7d8-c1d8107f478a" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherNoncashIncomeExpense_202b86c2-5d40-4db9-85c7-979ce763b445" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherNoncashIncomeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_0d75c686-c08e-4b35-ba0c-69c902e029aa" xlink:to="loc_us-gaap_OtherNoncashIncomeExpense_202b86c2-5d40-4db9-85c7-979ce763b445" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_bf743663-a2a9-4672-a0c2-f2b186bb0a69" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncreaseDecreaseInOperatingCapitalAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_0d75c686-c08e-4b35-ba0c-69c902e029aa" xlink:to="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_bf743663-a2a9-4672-a0c2-f2b186bb0a69" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInAccountsReceivable_18fb9722-c375-41df-989f-b8429f51d890" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncreaseDecreaseInAccountsReceivable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_bf743663-a2a9-4672-a0c2-f2b186bb0a69" xlink:to="loc_us-gaap_IncreaseDecreaseInAccountsReceivable_18fb9722-c375-41df-989f-b8429f51d890" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInInventories_75e7b527-7b07-4edd-a5cf-8a047d2dcf18" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncreaseDecreaseInInventories"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_bf743663-a2a9-4672-a0c2-f2b186bb0a69" xlink:to="loc_us-gaap_IncreaseDecreaseInInventories_75e7b527-7b07-4edd-a5cf-8a047d2dcf18" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInOtherCurrentAssets_d1d3acc3-b817-4c11-b99d-5628be053569" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncreaseDecreaseInOtherCurrentAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_bf743663-a2a9-4672-a0c2-f2b186bb0a69" xlink:to="loc_us-gaap_IncreaseDecreaseInOtherCurrentAssets_d1d3acc3-b817-4c11-b99d-5628be053569" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInAccountsPayable_1f44ac9c-52af-4e74-9c71-e338867d8e16" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncreaseDecreaseInAccountsPayable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_bf743663-a2a9-4672-a0c2-f2b186bb0a69" xlink:to="loc_us-gaap_IncreaseDecreaseInAccountsPayable_1f44ac9c-52af-4e74-9c71-e338867d8e16" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInAccruedLiabilities_b16be0f2-a3ad-452b-89ad-a83eeeb57b87" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncreaseDecreaseInAccruedLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_bf743663-a2a9-4672-a0c2-f2b186bb0a69" xlink:to="loc_us-gaap_IncreaseDecreaseInAccruedLiabilities_b16be0f2-a3ad-452b-89ad-a83eeeb57b87" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainLossRelatedToLitigationSettlement_3cff8ee5-e00b-474a-b886-f2a5bf9e135a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GainLossRelatedToLitigationSettlement"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_bf743663-a2a9-4672-a0c2-f2b186bb0a69" xlink:to="loc_us-gaap_GainLossRelatedToLitigationSettlement_3cff8ee5-e00b-474a-b886-f2a5bf9e135a" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInAccruedIncomeTaxesPayable_5c5e3145-80df-4009-bca6-af5a036dffef" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncreaseDecreaseInAccruedIncomeTaxesPayable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_bf743663-a2a9-4672-a0c2-f2b186bb0a69" xlink:to="loc_us-gaap_IncreaseDecreaseInAccruedIncomeTaxesPayable_5c5e3145-80df-4009-bca6-af5a036dffef" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInOtherNoncurrentLiabilities_af6bd1c2-1132-4f4e-8c56-88bf5b71fa10" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncreaseDecreaseInOtherNoncurrentLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_bf743663-a2a9-4672-a0c2-f2b186bb0a69" xlink:to="loc_us-gaap_IncreaseDecreaseInOtherNoncurrentLiabilities_af6bd1c2-1132-4f4e-8c56-88bf5b71fa10" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInOtherNoncurrentAssets_0f88b6d9-9df8-4488-ae71-22927d7e2220" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncreaseDecreaseInOtherNoncurrentAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_bf743663-a2a9-4672-a0c2-f2b186bb0a69" xlink:to="loc_us-gaap_IncreaseDecreaseInOtherNoncurrentAssets_0f88b6d9-9df8-4488-ae71-22927d7e2220" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_57539b73-4f65-43ed-b309-fbe0babafcd6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_77484741-345e-463f-b6ef-dea8846c3ecc" xlink:to="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_57539b73-4f65-43ed-b309-fbe0babafcd6" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_4c40deec-91bc-48bb-b9e9-f43ee5808c4d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_b2e950cf-6cb0-4839-be60-b5005cf330d3" xlink:to="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_4c40deec-91bc-48bb-b9e9-f43ee5808c4d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquirePropertyPlantAndEquipment_4ebbc3d0-58f8-4c48-b5f2-024a0037eec0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PaymentsToAcquirePropertyPlantAndEquipment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_4c40deec-91bc-48bb-b9e9-f43ee5808c4d" xlink:to="loc_us-gaap_PaymentsToAcquirePropertyPlantAndEquipment_4ebbc3d0-58f8-4c48-b5f2-024a0037eec0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsForProceedsFromOtherInvestingActivities_67ec5799-a8b5-478f-8fe0-e988fbcf2feb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PaymentsForProceedsFromOtherInvestingActivities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_4c40deec-91bc-48bb-b9e9-f43ee5808c4d" xlink:to="loc_us-gaap_PaymentsForProceedsFromOtherInvestingActivities_67ec5799-a8b5-478f-8fe0-e988fbcf2feb" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_6767be38-4d51-41ca-b960-a32315be9ef4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_4c40deec-91bc-48bb-b9e9-f43ee5808c4d" xlink:to="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_6767be38-4d51-41ca-b960-a32315be9ef4" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_946133d3-52bc-46f9-9775-405876d29ab1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_b2e950cf-6cb0-4839-be60-b5005cf330d3" xlink:to="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_946133d3-52bc-46f9-9775-405876d29ab1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromIssuanceOfLongTermDebt_b82d4daa-d43d-4153-9ed0-05481721d9e0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProceedsFromIssuanceOfLongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_946133d3-52bc-46f9-9775-405876d29ab1" xlink:to="loc_us-gaap_ProceedsFromIssuanceOfLongTermDebt_b82d4daa-d43d-4153-9ed0-05481721d9e0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_PaymentsOfDebtIssuanceCostsAndDebtDiscount_3f26e05b-a060-4446-b087-c438ea3b30dd" xlink:href="shc-20250630.xsd#shc_PaymentsOfDebtIssuanceCostsAndDebtDiscount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_946133d3-52bc-46f9-9775-405876d29ab1" xlink:to="loc_shc_PaymentsOfDebtIssuanceCostsAndDebtDiscount_3f26e05b-a060-4446-b087-c438ea3b30dd" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RepaymentsOfLongTermDebt_c76cf500-c378-4f6d-8db9-771d79eded74" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RepaymentsOfLongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_946133d3-52bc-46f9-9775-405876d29ab1" xlink:to="loc_us-gaap_RepaymentsOfLongTermDebt_c76cf500-c378-4f6d-8db9-771d79eded74" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_BuyoutOfLeasedFacility_af4eb5e1-fc82-4fc2-8de7-ca2cd9c029b9" xlink:href="shc-20250630.xsd#shc_BuyoutOfLeasedFacility"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_946133d3-52bc-46f9-9775-405876d29ab1" xlink:to="loc_shc_BuyoutOfLeasedFacility_af4eb5e1-fc82-4fc2-8de7-ca2cd9c029b9" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation_02f5717d-97b3-4ce4-897e-416975cdcc02" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_946133d3-52bc-46f9-9775-405876d29ab1" xlink:to="loc_us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation_02f5717d-97b3-4ce4-897e-416975cdcc02" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromPaymentsForOtherFinancingActivities_b11caa62-9591-49f4-872c-52baa8c6777e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProceedsFromPaymentsForOtherFinancingActivities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_946133d3-52bc-46f9-9775-405876d29ab1" xlink:to="loc_us-gaap_ProceedsFromPaymentsForOtherFinancingActivities_b11caa62-9591-49f4-872c-52baa8c6777e" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_b1c7a899-e1ee-4ea9-b60c-ff74290ad413" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_946133d3-52bc-46f9-9775-405876d29ab1" xlink:to="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_b1c7a899-e1ee-4ea9-b60c-ff74290ad413" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_cb9621cd-ccf8-4903-bd45-504824db59fa" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_b2e950cf-6cb0-4839-be60-b5005cf330d3" xlink:to="loc_us-gaap_EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_cb9621cd-ccf8-4903-bd45-504824db59fa" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_2586d4cc-6ed6-4150-ba54-031e89d40f9e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_b2e950cf-6cb0-4839-be60-b5005cf330d3" xlink:to="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_2586d4cc-6ed6-4150-ba54-031e89d40f9e" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_cbb1ed5e-2328-44a3-a626-0535bd146de8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_b2e950cf-6cb0-4839-be60-b5005cf330d3" xlink:to="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_cbb1ed5e-2328-44a3-a626-0535bd146de8" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_a41f7c09-3e47-466f-897d-a6dea532bd25" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SupplementalCashFlowInformationAbstract_05998f5e-a06e-4c72-a4c0-6f5b32cdaba5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SupplementalCashFlowInformationAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_b2e950cf-6cb0-4839-be60-b5005cf330d3" xlink:to="loc_us-gaap_SupplementalCashFlowInformationAbstract_05998f5e-a06e-4c72-a4c0-6f5b32cdaba5" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestPaidNet_9950387b-317a-489e-a05c-aca67eedcb58" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestPaidNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SupplementalCashFlowInformationAbstract_05998f5e-a06e-4c72-a4c0-6f5b32cdaba5" xlink:to="loc_us-gaap_InterestPaidNet_9950387b-317a-489e-a05c-aca67eedcb58" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxesPaidNet_5965915d-b914-4598-bba5-faa1134d2d8d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxesPaidNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SupplementalCashFlowInformationAbstract_05998f5e-a06e-4c72-a4c0-6f5b32cdaba5" xlink:to="loc_us-gaap_IncomeTaxesPaidNet_5965915d-b914-4598-bba5-faa1134d2d8d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CapitalExpendituresIncurredButNotYetPaid_c968254d-791f-4ed7-a158-85e47ad87fd4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CapitalExpendituresIncurredButNotYetPaid"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SupplementalCashFlowInformationAbstract_05998f5e-a06e-4c72-a4c0-6f5b32cdaba5" xlink:to="loc_us-gaap_CapitalExpendituresIncurredButNotYetPaid_c968254d-791f-4ed7-a158-85e47ad87fd4" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://soterahealth.com/role/ConsolidatedStatementsofEquity" xlink:type="simple" xlink:href="shc-20250630.xsd#ConsolidatedStatementsofEquity"/>
  <link:definitionLink xlink:role="http://soterahealth.com/role/ConsolidatedStatementsofEquity" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_8d3d3571-6201-4318-af8b-1f73c0e8eaf9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_6715639b-e96f-42c5-a736-d35ddf5b9a34" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_8d3d3571-6201-4318-af8b-1f73c0e8eaf9" xlink:to="loc_us-gaap_StatementTable_6715639b-e96f-42c5-a736-d35ddf5b9a34" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_588fc235-69dd-4349-ac22-6e49feef69ed" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_6715639b-e96f-42c5-a736-d35ddf5b9a34" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_588fc235-69dd-4349-ac22-6e49feef69ed" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_588fc235-69dd-4349-ac22-6e49feef69ed_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_588fc235-69dd-4349-ac22-6e49feef69ed" xlink:to="loc_us-gaap_EquityComponentDomain_588fc235-69dd-4349-ac22-6e49feef69ed_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_dafffc50-264b-49b0-95b1-92e9873f7e9c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_588fc235-69dd-4349-ac22-6e49feef69ed" xlink:to="loc_us-gaap_EquityComponentDomain_dafffc50-264b-49b0-95b1-92e9873f7e9c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_96d8ff4c-bc31-4248-9a7a-77caee345eba" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_dafffc50-264b-49b0-95b1-92e9873f7e9c" xlink:to="loc_us-gaap_CommonStockMember_96d8ff4c-bc31-4248-9a7a-77caee345eba" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockCommonMember_ba42905e-9e18-43f4-b980-6553b7857dc0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TreasuryStockCommonMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_dafffc50-264b-49b0-95b1-92e9873f7e9c" xlink:to="loc_us-gaap_TreasuryStockCommonMember_ba42905e-9e18-43f4-b980-6553b7857dc0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapitalMember_b9dd0086-ddbc-441e-b800-19e0c2a371bc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AdditionalPaidInCapitalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_dafffc50-264b-49b0-95b1-92e9873f7e9c" xlink:to="loc_us-gaap_AdditionalPaidInCapitalMember_b9dd0086-ddbc-441e-b800-19e0c2a371bc" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsMember_f9722cbe-fd0b-4bf2-bb32-6df5a805b585" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RetainedEarningsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_dafffc50-264b-49b0-95b1-92e9873f7e9c" xlink:to="loc_us-gaap_RetainedEarningsMember_f9722cbe-fd0b-4bf2-bb32-6df5a805b585" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_5930f128-930b-479b-b0bf-f8d5740893ca" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_dafffc50-264b-49b0-95b1-92e9873f7e9c" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_5930f128-930b-479b-b0bf-f8d5740893ca" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_6ac45d5e-902c-419a-bb17-acba8ae08301" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncreaseDecreaseInStockholdersEquityRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_8d3d3571-6201-4318-af8b-1f73c0e8eaf9" xlink:to="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_6ac45d5e-902c-419a-bb17-acba8ae08301" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_3869cd84-635c-41fd-b676-2ea945adb885" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_6ac45d5e-902c-419a-bb17-acba8ae08301" xlink:to="loc_us-gaap_CommonStockSharesOutstanding_3869cd84-635c-41fd-b676-2ea945adb885" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_d879528b-bb60-46f4-9c30-3688e159e23d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_6ac45d5e-902c-419a-bb17-acba8ae08301" xlink:to="loc_us-gaap_StockholdersEquity_d879528b-bb60-46f4-9c30-3688e159e23d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation_97dbf1c2-bc04-434c-bda2-a690fafe790f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_6ac45d5e-902c-419a-bb17-acba8ae08301" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation_97dbf1c2-bc04-434c-bda2-a690fafe790f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation_cde70db1-83eb-4e44-ae32-0d227ecd3d72" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_6ac45d5e-902c-419a-bb17-acba8ae08301" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation_cde70db1-83eb-4e44-ae32-0d227ecd3d72" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterestAbstract_f080d679-b79e-46c9-8f6a-bfe71e59f6d7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterestAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_6ac45d5e-902c-419a-bb17-acba8ae08301" xlink:to="loc_us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterestAbstract_f080d679-b79e-46c9-8f6a-bfe71e59f6d7" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax_54b236ee-0d96-4a39-847c-cc9ac5c23f73" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterestAbstract_f080d679-b79e-46c9-8f6a-bfe71e59f6d7" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax_54b236ee-0d96-4a39-847c-cc9ac5c23f73" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax_a6f82cea-0015-4263-a44c-dd1b08cb7e17" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterestAbstract_f080d679-b79e-46c9-8f6a-bfe71e59f6d7" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax_a6f82cea-0015-4263-a44c-dd1b08cb7e17" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTax_717c52f4-0c76-44d1-9570-7212075c56f8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterestAbstract_f080d679-b79e-46c9-8f6a-bfe71e59f6d7" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTax_717c52f4-0c76-44d1-9570-7212075c56f8" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_9b6ee59a-b4d7-483e-9009-90aa8f605b0b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterestAbstract_f080d679-b79e-46c9-8f6a-bfe71e59f6d7" xlink:to="loc_us-gaap_NetIncomeLoss_9b6ee59a-b4d7-483e-9009-90aa8f605b0b" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_646d53df-2208-4d04-a77a-f5b7367aebeb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_9908b917-6f4d-43e7-a6a9-9853ae0ef8e6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockholdersEquity"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://soterahealth.com/role/RevenueRecognitionDetails" xlink:type="simple" xlink:href="shc-20250630.xsd#RevenueRecognitionDetails"/>
  <link:definitionLink xlink:role="http://soterahealth.com/role/RevenueRecognitionDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueLineItems_d65872ae-f839-489f-bd00-a9662e491efe" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DisaggregationOfRevenueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueTable_8cfa68f4-96c4-499a-b249-f0e59461d806" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DisaggregationOfRevenueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_d65872ae-f839-489f-bd00-a9662e491efe" xlink:to="loc_us-gaap_DisaggregationOfRevenueTable_8cfa68f4-96c4-499a-b249-f0e59461d806" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_8b8eb419-974f-47ca-8f4c-1c45eeac85c2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_8cfa68f4-96c4-499a-b249-f0e59461d806" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_8b8eb419-974f-47ca-8f4c-1c45eeac85c2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_8b8eb419-974f-47ca-8f4c-1c45eeac85c2_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_8b8eb419-974f-47ca-8f4c-1c45eeac85c2" xlink:to="loc_us-gaap_SegmentDomain_8b8eb419-974f-47ca-8f4c-1c45eeac85c2_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_002e8a2a-0fd2-4be9-8c4a-25e153d2a162" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_8b8eb419-974f-47ca-8f4c-1c45eeac85c2" xlink:to="loc_us-gaap_SegmentDomain_002e8a2a-0fd2-4be9-8c4a-25e153d2a162" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_SterigenicsMember_0cc42ccf-d764-43a8-8532-2dff9bf538cb" xlink:href="shc-20250630.xsd#shc_SterigenicsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_002e8a2a-0fd2-4be9-8c4a-25e153d2a162" xlink:to="loc_shc_SterigenicsMember_0cc42ccf-d764-43a8-8532-2dff9bf538cb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_NordionMember_3ae81f3a-cce5-4571-ba59-a89e62940f09" xlink:href="shc-20250630.xsd#shc_NordionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_002e8a2a-0fd2-4be9-8c4a-25e153d2a162" xlink:to="loc_shc_NordionMember_3ae81f3a-cce5-4571-ba59-a89e62940f09" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_NelsonLabsMember_db66c181-daa8-45eb-ad05-2b2550163f5e" xlink:href="shc-20250630.xsd#shc_NelsonLabsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_002e8a2a-0fd2-4be9-8c4a-25e153d2a162" xlink:to="loc_shc_NelsonLabsMember_db66c181-daa8-45eb-ad05-2b2550163f5e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TimingOfTransferOfGoodOrServiceAxis_3b6b5727-1d3f-4a68-a2f0-0811537c7c3e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TimingOfTransferOfGoodOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_8cfa68f4-96c4-499a-b249-f0e59461d806" xlink:to="loc_us-gaap_TimingOfTransferOfGoodOrServiceAxis_3b6b5727-1d3f-4a68-a2f0-0811537c7c3e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TimingOfTransferOfGoodOrServiceDomain_3b6b5727-1d3f-4a68-a2f0-0811537c7c3e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TimingOfTransferOfGoodOrServiceDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_TimingOfTransferOfGoodOrServiceAxis_3b6b5727-1d3f-4a68-a2f0-0811537c7c3e" xlink:to="loc_us-gaap_TimingOfTransferOfGoodOrServiceDomain_3b6b5727-1d3f-4a68-a2f0-0811537c7c3e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TimingOfTransferOfGoodOrServiceDomain_32f0d3e6-21b0-42c5-941c-a8aa25194e29" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TimingOfTransferOfGoodOrServiceDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_TimingOfTransferOfGoodOrServiceAxis_3b6b5727-1d3f-4a68-a2f0-0811537c7c3e" xlink:to="loc_us-gaap_TimingOfTransferOfGoodOrServiceDomain_32f0d3e6-21b0-42c5-941c-a8aa25194e29" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransferredAtPointInTimeMember_e4c53f68-aaa7-431a-929e-c39431a35673" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TransferredAtPointInTimeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TimingOfTransferOfGoodOrServiceDomain_32f0d3e6-21b0-42c5-941c-a8aa25194e29" xlink:to="loc_us-gaap_TransferredAtPointInTimeMember_e4c53f68-aaa7-431a-929e-c39431a35673" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransferredOverTimeMember_44e7405d-850d-498d-90ec-5930a9074119" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TransferredOverTimeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TimingOfTransferOfGoodOrServiceDomain_32f0d3e6-21b0-42c5-941c-a8aa25194e29" xlink:to="loc_us-gaap_TransferredOverTimeMember_44e7405d-850d-498d-90ec-5930a9074119" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_b1b04e88-b01d-4b42-aff4-f7e628e56cec" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_d65872ae-f839-489f-bd00-a9662e491efe" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_b1b04e88-b01d-4b42-aff4-f7e628e56cec" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://soterahealth.com/role/GoodwillandOtherIntangibleAssetsScheduleofGoodwillDetails" xlink:type="simple" xlink:href="shc-20250630.xsd#GoodwillandOtherIntangibleAssetsScheduleofGoodwillDetails"/>
  <link:definitionLink xlink:role="http://soterahealth.com/role/GoodwillandOtherIntangibleAssetsScheduleofGoodwillDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GoodwillLineItems_30638955-b079-4deb-8dec-8da14ae1d551" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GoodwillLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfGoodwillTable_88c0621a-dbce-4ef6-a804-2c8f5770f476" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfGoodwillTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_GoodwillLineItems_30638955-b079-4deb-8dec-8da14ae1d551" xlink:to="loc_us-gaap_ScheduleOfGoodwillTable_88c0621a-dbce-4ef6-a804-2c8f5770f476" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_c1288e05-3257-48d3-a586-f4f6bd0f1120" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfGoodwillTable_88c0621a-dbce-4ef6-a804-2c8f5770f476" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_c1288e05-3257-48d3-a586-f4f6bd0f1120" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_c1288e05-3257-48d3-a586-f4f6bd0f1120_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_c1288e05-3257-48d3-a586-f4f6bd0f1120" xlink:to="loc_us-gaap_SegmentDomain_c1288e05-3257-48d3-a586-f4f6bd0f1120_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_b304f92d-0fbd-4574-9c0e-40bf9ab35f4e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_c1288e05-3257-48d3-a586-f4f6bd0f1120" xlink:to="loc_us-gaap_SegmentDomain_b304f92d-0fbd-4574-9c0e-40bf9ab35f4e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_SterigenicsMember_ec9f1878-0a91-4a8c-bcff-44eaf727c0dc" xlink:href="shc-20250630.xsd#shc_SterigenicsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_b304f92d-0fbd-4574-9c0e-40bf9ab35f4e" xlink:to="loc_shc_SterigenicsMember_ec9f1878-0a91-4a8c-bcff-44eaf727c0dc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_NordionMember_eaed00a5-8f84-4b45-ab6d-064fa7910995" xlink:href="shc-20250630.xsd#shc_NordionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_b304f92d-0fbd-4574-9c0e-40bf9ab35f4e" xlink:to="loc_shc_NordionMember_eaed00a5-8f84-4b45-ab6d-064fa7910995" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_NelsonLabsMember_f2dab140-f860-409e-904b-f945c5b2e05b" xlink:href="shc-20250630.xsd#shc_NelsonLabsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_b304f92d-0fbd-4574-9c0e-40bf9ab35f4e" xlink:to="loc_shc_NelsonLabsMember_f2dab140-f860-409e-904b-f945c5b2e05b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GoodwillRollForward_9002899f-89a1-42b5-aa8f-5d72db91add0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GoodwillRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GoodwillLineItems_30638955-b079-4deb-8dec-8da14ae1d551" xlink:to="loc_us-gaap_GoodwillRollForward_9002899f-89a1-42b5-aa8f-5d72db91add0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_d69a3c9f-b7da-482c-8742-18f0dea0b955" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_Goodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GoodwillRollForward_9002899f-89a1-42b5-aa8f-5d72db91add0" xlink:to="loc_us-gaap_Goodwill_d69a3c9f-b7da-482c-8742-18f0dea0b955" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GoodwillForeignCurrencyTranslationGainLoss_e43b0b68-f9e2-4e94-9567-bc33984db558" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GoodwillForeignCurrencyTranslationGainLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GoodwillRollForward_9002899f-89a1-42b5-aa8f-5d72db91add0" xlink:to="loc_us-gaap_GoodwillForeignCurrencyTranslationGainLoss_e43b0b68-f9e2-4e94-9567-bc33984db558" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_107c2ff7-0cbf-4793-ab28-cb385c59603a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_Goodwill"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://soterahealth.com/role/GoodwillandOtherIntangibleAssetsScheduleofAcquiredFiniteLivedandIndefiniteLivedIntangibleAssetsDetails" xlink:type="simple" xlink:href="shc-20250630.xsd#GoodwillandOtherIntangibleAssetsScheduleofAcquiredFiniteLivedandIndefiniteLivedIntangibleAssetsDetails"/>
  <link:definitionLink xlink:role="http://soterahealth.com/role/GoodwillandOtherIntangibleAssetsScheduleofAcquiredFiniteLivedandIndefiniteLivedIntangibleAssetsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_916d521a-df58-48b0-ab52-834e56e65665" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAcquiredFiniteLivedIntangibleAssetByMajorClassTable_aae723fe-e888-4e02-b2b4-66cbd3c6958c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfAcquiredFiniteLivedIntangibleAssetByMajorClassTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_916d521a-df58-48b0-ab52-834e56e65665" xlink:to="loc_us-gaap_ScheduleOfAcquiredFiniteLivedIntangibleAssetByMajorClassTable_aae723fe-e888-4e02-b2b4-66cbd3c6958c" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_5564d7de-1f34-4f7d-a584-3e0df4855584" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAcquiredFiniteLivedIntangibleAssetByMajorClassTable_aae723fe-e888-4e02-b2b4-66cbd3c6958c" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_5564d7de-1f34-4f7d-a584-3e0df4855584" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_5564d7de-1f34-4f7d-a584-3e0df4855584_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_5564d7de-1f34-4f7d-a584-3e0df4855584" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_5564d7de-1f34-4f7d-a584-3e0df4855584_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_753df4e3-33d4-4604-bf13-c85c13b9cc5f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_5564d7de-1f34-4f7d-a584-3e0df4855584" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_753df4e3-33d4-4604-bf13-c85c13b9cc5f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CustomerRelationshipsMember_deb6f63c-65b5-42e2-9fe1-fe7122e36ff3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CustomerRelationshipsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_753df4e3-33d4-4604-bf13-c85c13b9cc5f" xlink:to="loc_us-gaap_CustomerRelationshipsMember_deb6f63c-65b5-42e2-9fe1-fe7122e36ff3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DevelopedTechnologyRightsMember_16938f4a-e475-4ccd-a124-c29696a1e7e5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DevelopedTechnologyRightsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_753df4e3-33d4-4604-bf13-c85c13b9cc5f" xlink:to="loc_us-gaap_DevelopedTechnologyRightsMember_16938f4a-e475-4ccd-a124-c29696a1e7e5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TradeNamesMember_21f16d7a-1c83-467f-801b-8fde22fad16c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TradeNamesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_753df4e3-33d4-4604-bf13-c85c13b9cc5f" xlink:to="loc_us-gaap_TradeNamesMember_21f16d7a-1c83-467f-801b-8fde22fad16c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_LandUseRightsMember_4103c709-5cc6-45a9-8bd5-7ac405284c0f" xlink:href="shc-20250630.xsd#shc_LandUseRightsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_753df4e3-33d4-4604-bf13-c85c13b9cc5f" xlink:to="loc_shc_LandUseRightsMember_4103c709-5cc6-45a9-8bd5-7ac405284c0f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_SealedSourceAndSupplyAgreementsMember_faa99838-c8a0-477a-a248-9411d4ddcb26" xlink:href="shc-20250630.xsd#shc_SealedSourceAndSupplyAgreementsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_753df4e3-33d4-4604-bf13-c85c13b9cc5f" xlink:to="loc_shc_SealedSourceAndSupplyAgreementsMember_faa99838-c8a0-477a-a248-9411d4ddcb26" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherIntangibleAssetsMember_d9fd50cb-54fb-4d4a-9a4a-1ca438509ab2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherIntangibleAssetsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_753df4e3-33d4-4604-bf13-c85c13b9cc5f" xlink:to="loc_us-gaap_OtherIntangibleAssetsMember_d9fd50cb-54fb-4d4a-9a4a-1ca438509ab2" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsGross_d5d64a85-3164-40ba-a878-72975c363009" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_916d521a-df58-48b0-ab52-834e56e65665" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsGross_d5d64a85-3164-40ba-a878-72975c363009" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_5457c39f-ef40-405a-9b07-d7e0cc9e1648" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_916d521a-df58-48b0-ab52-834e56e65665" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_5457c39f-ef40-405a-9b07-d7e0cc9e1648" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AcquiredIndefiniteLivedIntangibleAssetsLineItems_959483c2-1efd-4d85-84c7-71b8cc5d3186" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AcquiredIndefiniteLivedIntangibleAssetsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAcquiredIndefiniteLivedIntangibleAssetsByMajorClassTable_5bc5e0ef-259e-4d18-acf5-c3af6ebf11fd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfAcquiredIndefiniteLivedIntangibleAssetsByMajorClassTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AcquiredIndefiniteLivedIntangibleAssetsLineItems_959483c2-1efd-4d85-84c7-71b8cc5d3186" xlink:to="loc_us-gaap_ScheduleOfAcquiredIndefiniteLivedIntangibleAssetsByMajorClassTable_5bc5e0ef-259e-4d18-acf5-c3af6ebf11fd" xlink:type="arc" order="2" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_8413473e-4d97-4bd4-b39e-6494e3f78d47" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAcquiredIndefiniteLivedIntangibleAssetsByMajorClassTable_5bc5e0ef-259e-4d18-acf5-c3af6ebf11fd" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_8413473e-4d97-4bd4-b39e-6494e3f78d47" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_8413473e-4d97-4bd4-b39e-6494e3f78d47_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_8413473e-4d97-4bd4-b39e-6494e3f78d47" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_8413473e-4d97-4bd4-b39e-6494e3f78d47_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_4c3d9bbb-98da-44dd-b060-ee117831b5bd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_8413473e-4d97-4bd4-b39e-6494e3f78d47" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_4c3d9bbb-98da-44dd-b060-ee117831b5bd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LicensingAgreementsMember_7dfc9e97-c22c-457c-8f2a-839db47ed0a9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LicensingAgreementsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_4c3d9bbb-98da-44dd-b060-ee117831b5bd" xlink:to="loc_us-gaap_LicensingAgreementsMember_7dfc9e97-c22c-457c-8f2a-839db47ed0a9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TrademarksAndTradeNamesMember_8d08b9fe-e07a-4c11-81bd-201ccb9aee1a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TrademarksAndTradeNamesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_4c3d9bbb-98da-44dd-b060-ee117831b5bd" xlink:to="loc_us-gaap_TrademarksAndTradeNamesMember_8d08b9fe-e07a-4c11-81bd-201ccb9aee1a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill_a4238a7e-34d3-4dde-adf8-d89eff380baf" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AcquiredIndefiniteLivedIntangibleAssetsLineItems_959483c2-1efd-4d85-84c7-71b8cc5d3186" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill_a4238a7e-34d3-4dde-adf8-d89eff380baf" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_LicensingAgreementsRenewalTerm_9a75eb86-5343-4f46-b1da-9da247869c69" xlink:href="shc-20250630.xsd#shc_LicensingAgreementsRenewalTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AcquiredIndefiniteLivedIntangibleAssetsLineItems_959483c2-1efd-4d85-84c7-71b8cc5d3186" xlink:to="loc_shc_LicensingAgreementsRenewalTerm_9a75eb86-5343-4f46-b1da-9da247869c69" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IntangibleAssetsGrossExcludingGoodwill_345c187c-2aa1-4703-bee9-6dee93b4d190" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IntangibleAssetsGrossExcludingGoodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AcquiredIndefiniteLivedIntangibleAssetsLineItems_959483c2-1efd-4d85-84c7-71b8cc5d3186" xlink:to="loc_us-gaap_IntangibleAssetsGrossExcludingGoodwill_345c187c-2aa1-4703-bee9-6dee93b4d190" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://soterahealth.com/role/GoodwillandOtherIntangibleAssetsNarrativeDetails" xlink:type="simple" xlink:href="shc-20250630.xsd#GoodwillandOtherIntangibleAssetsNarrativeDetails"/>
  <link:definitionLink xlink:role="http://soterahealth.com/role/GoodwillandOtherIntangibleAssetsNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_8dabe3be-39f4-439f-ae51-1004071b7cfc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_44d3d78b-f021-4bfd-8cc0-6a00305b7208" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_8dabe3be-39f4-439f-ae51-1004071b7cfc" xlink:to="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_44d3d78b-f021-4bfd-8cc0-6a00305b7208" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_0af0dba4-5ccc-41ca-8c36-276451bff1d9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_44d3d78b-f021-4bfd-8cc0-6a00305b7208" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_0af0dba4-5ccc-41ca-8c36-276451bff1d9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_0af0dba4-5ccc-41ca-8c36-276451bff1d9_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_0af0dba4-5ccc-41ca-8c36-276451bff1d9" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_0af0dba4-5ccc-41ca-8c36-276451bff1d9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_320d84fc-ab16-471d-a044-80df593adfb9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_0af0dba4-5ccc-41ca-8c36-276451bff1d9" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_320d84fc-ab16-471d-a044-80df593adfb9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherIntangibleAssetsMember_09e4d43f-287b-41b6-b59b-90945cb87e60" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherIntangibleAssetsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_320d84fc-ab16-471d-a044-80df593adfb9" xlink:to="loc_us-gaap_OtherIntangibleAssetsMember_09e4d43f-287b-41b6-b59b-90945cb87e60" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationAxis_ec1bf600-51cf-41f4-8643-120e307205aa" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeStatementLocationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_44d3d78b-f021-4bfd-8cc0-6a00305b7208" xlink:to="loc_us-gaap_IncomeStatementLocationAxis_ec1bf600-51cf-41f4-8643-120e307205aa" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_ec1bf600-51cf-41f4-8643-120e307205aa_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_ec1bf600-51cf-41f4-8643-120e307205aa" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_ec1bf600-51cf-41f4-8643-120e307205aa_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_194ebda0-fb2d-4bf5-b5e4-499ef9cf371b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_ec1bf600-51cf-41f4-8643-120e307205aa" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_194ebda0-fb2d-4bf5-b5e4-499ef9cf371b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_AmortizationOfIntangibleAssetsNonproductionMember_1889fd64-fe4a-45a9-aecd-62d491fcc3fd" xlink:href="shc-20250630.xsd#shc_AmortizationOfIntangibleAssetsNonproductionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_194ebda0-fb2d-4bf5-b5e4-499ef9cf371b" xlink:to="loc_shc_AmortizationOfIntangibleAssetsNonproductionMember_1889fd64-fe4a-45a9-aecd-62d491fcc3fd" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AmortizationOfIntangibleAssets_6d098650-2290-4506-ad33-ed3bd6bbb2f2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AmortizationOfIntangibleAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_8dabe3be-39f4-439f-ae51-1004071b7cfc" xlink:to="loc_us-gaap_AmortizationOfIntangibleAssets_6d098650-2290-4506-ad33-ed3bd6bbb2f2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsRemainingAmortizationPeriod1_259e1a89-370c-464e-b980-1797b5cf7835" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsRemainingAmortizationPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_8dabe3be-39f4-439f-ae51-1004071b7cfc" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsRemainingAmortizationPeriod1_259e1a89-370c-464e-b980-1797b5cf7835" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://soterahealth.com/role/GoodwillandOtherIntangibleAssetsScheduleofFiniteLivedIntangibleAssetsDetails" xlink:type="simple" xlink:href="shc-20250630.xsd#GoodwillandOtherIntangibleAssetsScheduleofFiniteLivedIntangibleAssetsDetails"/>
  <link:definitionLink xlink:role="http://soterahealth.com/role/GoodwillandOtherIntangibleAssetsScheduleofFiniteLivedIntangibleAssetsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_e5681c0e-b997-4b7f-bed4-13e2fdce86d3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAcquiredFiniteLivedIntangibleAssetByMajorClassTable_7d8a19c4-515f-46a5-b30d-8ea14560f82a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfAcquiredFiniteLivedIntangibleAssetByMajorClassTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_e5681c0e-b997-4b7f-bed4-13e2fdce86d3" xlink:to="loc_us-gaap_ScheduleOfAcquiredFiniteLivedIntangibleAssetByMajorClassTable_7d8a19c4-515f-46a5-b30d-8ea14560f82a" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_caac1dce-aa95-4102-b6de-facf70bb40fd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAcquiredFiniteLivedIntangibleAssetByMajorClassTable_7d8a19c4-515f-46a5-b30d-8ea14560f82a" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_caac1dce-aa95-4102-b6de-facf70bb40fd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_caac1dce-aa95-4102-b6de-facf70bb40fd_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_caac1dce-aa95-4102-b6de-facf70bb40fd" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_caac1dce-aa95-4102-b6de-facf70bb40fd_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_923deaca-a86d-4935-98f8-8faf9917abf2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_caac1dce-aa95-4102-b6de-facf70bb40fd" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_923deaca-a86d-4935-98f8-8faf9917abf2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CustomerRelationshipsMember_6fef96f6-eca5-468c-9b78-7a4601810c77" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CustomerRelationshipsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_923deaca-a86d-4935-98f8-8faf9917abf2" xlink:to="loc_us-gaap_CustomerRelationshipsMember_6fef96f6-eca5-468c-9b78-7a4601810c77" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DevelopedTechnologyRightsMember_34bd0258-b2e8-4bd8-98ff-a2f51b5d60d2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DevelopedTechnologyRightsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_923deaca-a86d-4935-98f8-8faf9917abf2" xlink:to="loc_us-gaap_DevelopedTechnologyRightsMember_34bd0258-b2e8-4bd8-98ff-a2f51b5d60d2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TradeNamesMember_ac9a154d-eb93-43ab-8cb6-c6370d3c0015" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TradeNamesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_923deaca-a86d-4935-98f8-8faf9917abf2" xlink:to="loc_us-gaap_TradeNamesMember_ac9a154d-eb93-43ab-8cb6-c6370d3c0015" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_LandUseRightsMember_64ed35b2-70f1-44a0-a0c8-762327c1969d" xlink:href="shc-20250630.xsd#shc_LandUseRightsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_923deaca-a86d-4935-98f8-8faf9917abf2" xlink:to="loc_shc_LandUseRightsMember_64ed35b2-70f1-44a0-a0c8-762327c1969d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_SealedSourceAndSupplyAgreementsMember_39af8547-0526-47c6-a10a-9aba76ea44d5" xlink:href="shc-20250630.xsd#shc_SealedSourceAndSupplyAgreementsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_923deaca-a86d-4935-98f8-8faf9917abf2" xlink:to="loc_shc_SealedSourceAndSupplyAgreementsMember_39af8547-0526-47c6-a10a-9aba76ea44d5" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherIntangibleAssetsMember_b6575bf2-354a-4994-bf69-18f7a3c88bf8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherIntangibleAssetsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_923deaca-a86d-4935-98f8-8faf9917abf2" xlink:to="loc_us-gaap_OtherIntangibleAssetsMember_b6575bf2-354a-4994-bf69-18f7a3c88bf8" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsRemainingAmortizationPeriod1_30dc1c6b-3292-4187-9d01-721181c68b6e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsRemainingAmortizationPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_e5681c0e-b997-4b7f-bed4-13e2fdce86d3" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsRemainingAmortizationPeriod1_30dc1c6b-3292-4187-9d01-721181c68b6e" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://soterahealth.com/role/LongTermDebtScheduleofLongtermDebtInstrumentsDetails" xlink:type="simple" xlink:href="shc-20250630.xsd#LongTermDebtScheduleofLongtermDebtInstrumentsDetails"/>
  <link:definitionLink xlink:role="http://soterahealth.com/role/LongTermDebtScheduleofLongtermDebtInstrumentsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_81a4e7c1-2d19-4ea0-8f22-59b4ea37a36b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_a025628f-884d-418e-ad68-0163bea84484" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_81a4e7c1-2d19-4ea0-8f22-59b4ea37a36b" xlink:to="loc_us-gaap_DebtInstrumentTable_a025628f-884d-418e-ad68-0163bea84484" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_bf626392-bcb0-4f78-af9f-c6972a841876" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_a025628f-884d-418e-ad68-0163bea84484" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_bf626392-bcb0-4f78-af9f-c6972a841876" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_bf626392-bcb0-4f78-af9f-c6972a841876_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_bf626392-bcb0-4f78-af9f-c6972a841876" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_bf626392-bcb0-4f78-af9f-c6972a841876_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_408f94d9-ebde-45b4-bc2d-e7e36e0b906b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_bf626392-bcb0-4f78-af9f-c6972a841876" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_408f94d9-ebde-45b4-bc2d-e7e36e0b906b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuredDebtMember_7a7558a5-fec9-426d-8255-e8f5a58fb3ae" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SecuredDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_408f94d9-ebde-45b4-bc2d-e7e36e0b906b" xlink:to="loc_us-gaap_SecuredDebtMember_7a7558a5-fec9-426d-8255-e8f5a58fb3ae" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_3b035637-7b63-4271-9fa8-79ea2041e35f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_a025628f-884d-418e-ad68-0163bea84484" xlink:to="loc_us-gaap_DebtInstrumentAxis_3b035637-7b63-4271-9fa8-79ea2041e35f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_3b035637-7b63-4271-9fa8-79ea2041e35f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_3b035637-7b63-4271-9fa8-79ea2041e35f" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_3b035637-7b63-4271-9fa8-79ea2041e35f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_ac0be38f-fce5-47a0-8ab9-20c1106ce32a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_3b035637-7b63-4271-9fa8-79ea2041e35f" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_ac0be38f-fce5-47a0-8ab9-20c1106ce32a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_SeniorSecuredNotesDue2031Member_5f77d350-5ed9-4f6e-9947-9bc7fa6596ab" xlink:href="shc-20250630.xsd#shc_SeniorSecuredNotesDue2031Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_ac0be38f-fce5-47a0-8ab9-20c1106ce32a" xlink:to="loc_shc_SeniorSecuredNotesDue2031Member_5f77d350-5ed9-4f6e-9947-9bc7fa6596ab" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_TermLoanDue2031Member_055bffa5-32b4-4122-b230-d2fc679164e7" xlink:href="shc-20250630.xsd#shc_TermLoanDue2031Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_ac0be38f-fce5-47a0-8ab9-20c1106ce32a" xlink:to="loc_shc_TermLoanDue2031Member_055bffa5-32b4-4122-b230-d2fc679164e7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentCarryingAmount_0f2454ad-92ce-447d-8b69-1fe0a68343b4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentCarryingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_81a4e7c1-2d19-4ea0-8f22-59b4ea37a36b" xlink:to="loc_us-gaap_DebtInstrumentCarryingAmount_0f2454ad-92ce-447d-8b69-1fe0a68343b4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_LongTermDebtCurrentMaturitiesGross_726515af-e835-4960-814b-8923b6588290" xlink:href="shc-20250630.xsd#shc_LongTermDebtCurrentMaturitiesGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_81a4e7c1-2d19-4ea0-8f22-59b4ea37a36b" xlink:to="loc_shc_LongTermDebtCurrentMaturitiesGross_726515af-e835-4960-814b-8923b6588290" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_LongTermDebtGrossNoncurrent_67a8cd76-3632-48a5-a0d8-36f1f4b72b40" xlink:href="shc-20250630.xsd#shc_LongTermDebtGrossNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_81a4e7c1-2d19-4ea0-8f22-59b4ea37a36b" xlink:to="loc_shc_LongTermDebtGrossNoncurrent_67a8cd76-3632-48a5-a0d8-36f1f4b72b40" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredFinanceCostsNoncurrentNet_d65d3399-53d1-47ff-9de4-9829613b2434" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DeferredFinanceCostsNoncurrentNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_81a4e7c1-2d19-4ea0-8f22-59b4ea37a36b" xlink:to="loc_us-gaap_DeferredFinanceCostsNoncurrentNet_d65d3399-53d1-47ff-9de4-9829613b2434" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredFinanceCostsCurrentNet_37e2ade8-4e84-47a9-ad8f-c5619bdba5f9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DeferredFinanceCostsCurrentNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_81a4e7c1-2d19-4ea0-8f22-59b4ea37a36b" xlink:to="loc_us-gaap_DeferredFinanceCostsCurrentNet_37e2ade8-4e84-47a9-ad8f-c5619bdba5f9" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredFinanceCostsNet_6954e046-2e98-45f2-8d7b-0515fc8834ae" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DeferredFinanceCostsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_81a4e7c1-2d19-4ea0-8f22-59b4ea37a36b" xlink:to="loc_us-gaap_DeferredFinanceCostsNet_6954e046-2e98-45f2-8d7b-0515fc8834ae" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentUnamortizedDiscount_f652e42c-a15d-4465-b565-77c87e29edb2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentUnamortizedDiscount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_81a4e7c1-2d19-4ea0-8f22-59b4ea37a36b" xlink:to="loc_us-gaap_DebtInstrumentUnamortizedDiscount_f652e42c-a15d-4465-b565-77c87e29edb2" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_DebtInstrumentUnamortizedDiscountExcludingCurrentPortion_2028ff6b-a16b-4542-aa67-8d38833892dc" xlink:href="shc-20250630.xsd#shc_DebtInstrumentUnamortizedDiscountExcludingCurrentPortion"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_81a4e7c1-2d19-4ea0-8f22-59b4ea37a36b" xlink:to="loc_shc_DebtInstrumentUnamortizedDiscountExcludingCurrentPortion_2028ff6b-a16b-4542-aa67-8d38833892dc" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentUnamortizedDiscountCurrent_bb8b96d1-dd30-44b1-b849-0f6a11bf634b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentUnamortizedDiscountCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_81a4e7c1-2d19-4ea0-8f22-59b4ea37a36b" xlink:to="loc_us-gaap_DebtInstrumentUnamortizedDiscountCurrent_bb8b96d1-dd30-44b1-b849-0f6a11bf634b" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebt_b38fdd34-cf07-453c-b320-370b63729cdb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_81a4e7c1-2d19-4ea0-8f22-59b4ea37a36b" xlink:to="loc_us-gaap_LongTermDebt_b38fdd34-cf07-453c-b320-370b63729cdb" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtCurrent_01008cc1-f02c-4fa7-9a53-d33b1f3670fb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongTermDebtCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_81a4e7c1-2d19-4ea0-8f22-59b4ea37a36b" xlink:to="loc_us-gaap_LongTermDebtCurrent_01008cc1-f02c-4fa7-9a53-d33b1f3670fb" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtNoncurrent_f58450aa-6513-4f6a-a224-4a5d8e8fe03f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongTermDebtNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_81a4e7c1-2d19-4ea0-8f22-59b4ea37a36b" xlink:to="loc_us-gaap_LongTermDebtNoncurrent_f58450aa-6513-4f6a-a224-4a5d8e8fe03f" xlink:type="arc" order="11"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://soterahealth.com/role/LongTermDebtSeniorSecuredCreditFacilitiesNarrativeDetails" xlink:type="simple" xlink:href="shc-20250630.xsd#LongTermDebtSeniorSecuredCreditFacilitiesNarrativeDetails"/>
  <link:definitionLink xlink:role="http://soterahealth.com/role/LongTermDebtSeniorSecuredCreditFacilitiesNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_22655bb2-1c72-4782-81d8-4f7aced28cb4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_f8bd5b55-dbe9-4432-9aff-6dc4bbaba8fe" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_22655bb2-1c72-4782-81d8-4f7aced28cb4" xlink:to="loc_us-gaap_DebtInstrumentTable_f8bd5b55-dbe9-4432-9aff-6dc4bbaba8fe" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityAxis_ee11f812-8aa3-4350-ad3d-105af600bc87" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CreditFacilityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_f8bd5b55-dbe9-4432-9aff-6dc4bbaba8fe" xlink:to="loc_us-gaap_CreditFacilityAxis_ee11f812-8aa3-4350-ad3d-105af600bc87" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_ee11f812-8aa3-4350-ad3d-105af600bc87_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_ee11f812-8aa3-4350-ad3d-105af600bc87" xlink:to="loc_us-gaap_CreditFacilityDomain_ee11f812-8aa3-4350-ad3d-105af600bc87_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_acd626be-1798-4634-a89c-700b5abc55c6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_ee11f812-8aa3-4350-ad3d-105af600bc87" xlink:to="loc_us-gaap_CreditFacilityDomain_acd626be-1798-4634-a89c-700b5abc55c6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_750a1dd8-a8aa-43a3-b3c9-8d4a6435ab87" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevolvingCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_acd626be-1798-4634-a89c-700b5abc55c6" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_750a1dd8-a8aa-43a3-b3c9-8d4a6435ab87" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LetterOfCreditMember_e9453509-930d-46b3-9eb8-40012b896650" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LetterOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_acd626be-1798-4634-a89c-700b5abc55c6" xlink:to="loc_us-gaap_LetterOfCreditMember_e9453509-930d-46b3-9eb8-40012b896650" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditMember_cbaf39b2-5ad1-45fc-ba20-fd91b0855790" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LineOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_acd626be-1798-4634-a89c-700b5abc55c6" xlink:to="loc_us-gaap_LineOfCreditMember_cbaf39b2-5ad1-45fc-ba20-fd91b0855790" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_ce196527-9413-4107-adb0-5466de6cf68b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_f8bd5b55-dbe9-4432-9aff-6dc4bbaba8fe" xlink:to="loc_us-gaap_DebtInstrumentAxis_ce196527-9413-4107-adb0-5466de6cf68b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_ce196527-9413-4107-adb0-5466de6cf68b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_ce196527-9413-4107-adb0-5466de6cf68b" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_ce196527-9413-4107-adb0-5466de6cf68b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_8692abfc-fc66-4449-8005-22c8f625e839" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_ce196527-9413-4107-adb0-5466de6cf68b" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_8692abfc-fc66-4449-8005-22c8f625e839" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_SeniorSecuredCreditFacilitiesMember_7d698ae0-3c55-4675-9771-b34e0ba92e40" xlink:href="shc-20250630.xsd#shc_SeniorSecuredCreditFacilitiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_8692abfc-fc66-4449-8005-22c8f625e839" xlink:to="loc_shc_SeniorSecuredCreditFacilitiesMember_7d698ae0-3c55-4675-9771-b34e0ba92e40" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_SeniorSecuredNotesDue2031Member_a790f1e4-57ce-4190-9c2f-8005794b8d2a" xlink:href="shc-20250630.xsd#shc_SeniorSecuredNotesDue2031Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_8692abfc-fc66-4449-8005-22c8f625e839" xlink:to="loc_shc_SeniorSecuredNotesDue2031Member_a790f1e4-57ce-4190-9c2f-8005794b8d2a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_TermLoanDue2026Member_11ea35d6-b1c9-4575-a057-a46cc70d9e1f" xlink:href="shc-20250630.xsd#shc_TermLoanDue2026Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_8692abfc-fc66-4449-8005-22c8f625e839" xlink:to="loc_shc_TermLoanDue2026Member_11ea35d6-b1c9-4575-a057-a46cc70d9e1f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_TermLoanBDue2026Member_3d4cb4e2-fc74-48f6-acf3-806d2b966d0b" xlink:href="shc-20250630.xsd#shc_TermLoanBDue2026Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_8692abfc-fc66-4449-8005-22c8f625e839" xlink:to="loc_shc_TermLoanBDue2026Member_3d4cb4e2-fc74-48f6-acf3-806d2b966d0b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateAxis_3f1bc74d-1640-4bed-9f09-c3ef916f7481" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_VariableRateAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_f8bd5b55-dbe9-4432-9aff-6dc4bbaba8fe" xlink:to="loc_us-gaap_VariableRateAxis_3f1bc74d-1640-4bed-9f09-c3ef916f7481" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateDomain_3f1bc74d-1640-4bed-9f09-c3ef916f7481_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_VariableRateDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_VariableRateAxis_3f1bc74d-1640-4bed-9f09-c3ef916f7481" xlink:to="loc_us-gaap_VariableRateDomain_3f1bc74d-1640-4bed-9f09-c3ef916f7481_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateDomain_fa49b782-361d-42c6-962f-9b8b15910b73" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_VariableRateDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_VariableRateAxis_3f1bc74d-1640-4bed-9f09-c3ef916f7481" xlink:to="loc_us-gaap_VariableRateDomain_fa49b782-361d-42c6-962f-9b8b15910b73" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BaseRateMember_f1a78a44-1c1b-4474-9669-9056168312bd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BaseRateMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableRateDomain_fa49b782-361d-42c6-962f-9b8b15910b73" xlink:to="loc_us-gaap_BaseRateMember_f1a78a44-1c1b-4474-9669-9056168312bd" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuredOvernightFinancingRateSofrMember_69645a33-d009-430d-88f1-39e323e73270" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SecuredOvernightFinancingRateSofrMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableRateDomain_fa49b782-361d-42c6-962f-9b8b15910b73" xlink:to="loc_us-gaap_SecuredOvernightFinancingRateSofrMember_69645a33-d009-430d-88f1-39e323e73270" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_0e2d574b-cc2f-4021-a3fe-cdb7a00bc837" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_f8bd5b55-dbe9-4432-9aff-6dc4bbaba8fe" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_0e2d574b-cc2f-4021-a3fe-cdb7a00bc837" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_0e2d574b-cc2f-4021-a3fe-cdb7a00bc837_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_0e2d574b-cc2f-4021-a3fe-cdb7a00bc837" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_0e2d574b-cc2f-4021-a3fe-cdb7a00bc837_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_a4931601-ea12-4e2a-bab1-01104f8c3479" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_0e2d574b-cc2f-4021-a3fe-cdb7a00bc837" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_a4931601-ea12-4e2a-bab1-01104f8c3479" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuredDebtMember_1f7b9af1-4204-4786-9bab-dbe4083cc028" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SecuredDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_a4931601-ea12-4e2a-bab1-01104f8c3479" xlink:to="loc_us-gaap_SecuredDebtMember_1f7b9af1-4204-4786-9bab-dbe4083cc028" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SeniorNotesMember_4c7bba2f-3f7f-4711-983c-c7aaeadb5093" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SeniorNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_a4931601-ea12-4e2a-bab1-01104f8c3479" xlink:to="loc_us-gaap_SeniorNotesMember_4c7bba2f-3f7f-4711-983c-c7aaeadb5093" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPeriodAxis_18edad4d-dcdd-40f1-ab3e-ba63107095c0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentRedemptionPeriodAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_f8bd5b55-dbe9-4432-9aff-6dc4bbaba8fe" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodAxis_18edad4d-dcdd-40f1-ab3e-ba63107095c0" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_18edad4d-dcdd-40f1-ab3e-ba63107095c0_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentRedemptionPeriodDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodAxis_18edad4d-dcdd-40f1-ab3e-ba63107095c0" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_18edad4d-dcdd-40f1-ab3e-ba63107095c0_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_fd5020f6-f638-419c-9788-ff46bd3f2c4d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentRedemptionPeriodDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodAxis_18edad4d-dcdd-40f1-ab3e-ba63107095c0" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_fd5020f6-f638-419c-9788-ff46bd3f2c4d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPeriodOneMember_092fc2a4-a832-4bfa-9def-329514f4b374" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentRedemptionPeriodOneMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_fd5020f6-f638-419c-9788-ff46bd3f2c4d" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodOneMember_092fc2a4-a832-4bfa-9def-329514f4b374" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPeriodTwoMember_5b164bac-adfe-464f-801b-3da47c70c453" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentRedemptionPeriodTwoMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_fd5020f6-f638-419c-9788-ff46bd3f2c4d" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodTwoMember_5b164bac-adfe-464f-801b-3da47c70c453" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_9ec729fd-9d7e-41c7-8b1f-265c20357abc" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_f8bd5b55-dbe9-4432-9aff-6dc4bbaba8fe" xlink:to="loc_srt_RangeAxis_9ec729fd-9d7e-41c7-8b1f-265c20357abc" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_9ec729fd-9d7e-41c7-8b1f-265c20357abc_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_9ec729fd-9d7e-41c7-8b1f-265c20357abc" xlink:to="loc_srt_RangeMember_9ec729fd-9d7e-41c7-8b1f-265c20357abc_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_3b395a16-0cee-4b71-8977-1915a641f868" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_9ec729fd-9d7e-41c7-8b1f-265c20357abc" xlink:to="loc_srt_RangeMember_3b395a16-0cee-4b71-8977-1915a641f868" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_726e07d0-ab61-4c7d-bb78-96a67cb340f0" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_3b395a16-0cee-4b71-8977-1915a641f868" xlink:to="loc_srt_MaximumMember_726e07d0-ab61-4c7d-bb78-96a67cb340f0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_LitigationCaseAxis_9e9ba74b-b32a-4825-bec0-2ab0e13fe949" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_LitigationCaseAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_f8bd5b55-dbe9-4432-9aff-6dc4bbaba8fe" xlink:to="loc_srt_LitigationCaseAxis_9e9ba74b-b32a-4825-bec0-2ab0e13fe949" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_LitigationCaseTypeDomain_9e9ba74b-b32a-4825-bec0-2ab0e13fe949_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_LitigationCaseTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_LitigationCaseAxis_9e9ba74b-b32a-4825-bec0-2ab0e13fe949" xlink:to="loc_srt_LitigationCaseTypeDomain_9e9ba74b-b32a-4825-bec0-2ab0e13fe949_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_LitigationCaseTypeDomain_5f6acbfb-22fb-4a66-ab58-9e60381bc715" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_LitigationCaseTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_LitigationCaseAxis_9e9ba74b-b32a-4825-bec0-2ab0e13fe949" xlink:to="loc_srt_LitigationCaseTypeDomain_5f6acbfb-22fb-4a66-ab58-9e60381bc715" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_EthyleneOxideTortLitigationIllinoisMember_7da3fe31-7dd3-4749-9515-ba7d70012950" xlink:href="shc-20250630.xsd#shc_EthyleneOxideTortLitigationIllinoisMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_LitigationCaseTypeDomain_5f6acbfb-22fb-4a66-ab58-9e60381bc715" xlink:to="loc_shc_EthyleneOxideTortLitigationIllinoisMember_7da3fe31-7dd3-4749-9515-ba7d70012950" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LitigationStatusAxis_8fe9811b-fcef-4fd8-b416-c4a9834bd924" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LitigationStatusAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_f8bd5b55-dbe9-4432-9aff-6dc4bbaba8fe" xlink:to="loc_us-gaap_LitigationStatusAxis_8fe9811b-fcef-4fd8-b416-c4a9834bd924" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LitigationStatusDomain_8fe9811b-fcef-4fd8-b416-c4a9834bd924_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LitigationStatusDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LitigationStatusAxis_8fe9811b-fcef-4fd8-b416-c4a9834bd924" xlink:to="loc_us-gaap_LitigationStatusDomain_8fe9811b-fcef-4fd8-b416-c4a9834bd924_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LitigationStatusDomain_69809651-7d4e-4687-afb6-3fcb125c5d48" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LitigationStatusDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LitigationStatusAxis_8fe9811b-fcef-4fd8-b416-c4a9834bd924" xlink:to="loc_us-gaap_LitigationStatusDomain_69809651-7d4e-4687-afb6-3fcb125c5d48" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PendingLitigationMember_5089427a-a882-496b-9f1a-4aefa7b0e7fe" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PendingLitigationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LitigationStatusDomain_69809651-7d4e-4687-afb6-3fcb125c5d48" xlink:to="loc_us-gaap_PendingLitigationMember_5089427a-a882-496b-9f1a-4aefa7b0e7fe" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_19a3f5d7-60bf-4eaf-89ff-34de6b2c3c33" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_22655bb2-1c72-4782-81d8-4f7aced28cb4" xlink:to="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_19a3f5d7-60bf-4eaf-89ff-34de6b2c3c33" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_LineOfCreditFacilityIncreaseInBorrowingCapacity_d57cdc6b-057b-4918-9451-d067f69263a9" xlink:href="shc-20250630.xsd#shc_LineOfCreditFacilityIncreaseInBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_22655bb2-1c72-4782-81d8-4f7aced28cb4" xlink:to="loc_shc_LineOfCreditFacilityIncreaseInBorrowingCapacity_d57cdc6b-057b-4918-9451-d067f69263a9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_69be896f-51ce-4af9-8f34-14da8c906019" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentBasisSpreadOnVariableRate1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_22655bb2-1c72-4782-81d8-4f7aced28cb4" xlink:to="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_69be896f-51ce-4af9-8f34-14da8c906019" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_DebtInstrumentApplicableFloorInterestRate_6fc8b030-0176-4dcc-adae-4c902e2b2c92" xlink:href="shc-20250630.xsd#shc_DebtInstrumentApplicableFloorInterestRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_22655bb2-1c72-4782-81d8-4f7aced28cb4" xlink:to="loc_shc_DebtInstrumentApplicableFloorInterestRate_6fc8b030-0176-4dcc-adae-4c902e2b2c92" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_DebtInstrumentPricingStepDownPercent_648c3141-2971-463e-824b-5eca8fad04a1" xlink:href="shc-20250630.xsd#shc_DebtInstrumentPricingStepDownPercent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_22655bb2-1c72-4782-81d8-4f7aced28cb4" xlink:to="loc_shc_DebtInstrumentPricingStepDownPercent_648c3141-2971-463e-824b-5eca8fad04a1" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_DebtInstrumentCovenantLeverageRatio_9b934592-b43c-4d8a-8d1f-5600c632a2a1" xlink:href="shc-20250630.xsd#shc_DebtInstrumentCovenantLeverageRatio"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_22655bb2-1c72-4782-81d8-4f7aced28cb4" xlink:to="loc_shc_DebtInstrumentCovenantLeverageRatio_9b934592-b43c-4d8a-8d1f-5600c632a2a1" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_DebtInstrumentSoftCallPremiumPercent_d6702a90-797f-46ed-a9c5-52de43bf6e62" xlink:href="shc-20250630.xsd#shc_DebtInstrumentSoftCallPremiumPercent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_22655bb2-1c72-4782-81d8-4f7aced28cb4" xlink:to="loc_shc_DebtInstrumentSoftCallPremiumPercent_d6702a90-797f-46ed-a9c5-52de43bf6e62" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateDuringPeriod_249090de-6977-4a31-a4e7-f47c5f342692" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentInterestRateDuringPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_22655bb2-1c72-4782-81d8-4f7aced28cb4" xlink:to="loc_us-gaap_DebtInstrumentInterestRateDuringPeriod_249090de-6977-4a31-a4e7-f47c5f342692" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentFaceAmount_edb84fbd-ad1e-4ec2-9c2f-f6ba8245f461" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentFaceAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_22655bb2-1c72-4782-81d8-4f7aced28cb4" xlink:to="loc_us-gaap_DebtInstrumentFaceAmount_edb84fbd-ad1e-4ec2-9c2f-f6ba8245f461" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_26b351bf-2d8a-4132-81de-d948626b6c28" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_22655bb2-1c72-4782-81d8-4f7aced28cb4" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_26b351bf-2d8a-4132-81de-d948626b6c28" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPricePercentage_aa5027ac-f55f-4ae4-9265-ea112e5aadd1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentRedemptionPricePercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_22655bb2-1c72-4782-81d8-4f7aced28cb4" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPricePercentage_aa5027ac-f55f-4ae4-9265-ea112e5aadd1" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPricePercentageOfPrincipalAmountRedeemed_c86e304f-2480-405c-b196-b6775d07037e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentRedemptionPricePercentageOfPrincipalAmountRedeemed"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_22655bb2-1c72-4782-81d8-4f7aced28cb4" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPricePercentageOfPrincipalAmountRedeemed_c86e304f-2480-405c-b196-b6775d07037e" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_DebtInstrumentRedemptionPricePercentageProceedsFromEquityOfferings_e0caa748-329e-4975-8dba-6e41b8b53e61" xlink:href="shc-20250630.xsd#shc_DebtInstrumentRedemptionPricePercentageProceedsFromEquityOfferings"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_22655bb2-1c72-4782-81d8-4f7aced28cb4" xlink:to="loc_shc_DebtInstrumentRedemptionPricePercentageProceedsFromEquityOfferings_e0caa748-329e-4975-8dba-6e41b8b53e61" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_DebtInstrumentRedemptionAsPercentOfOutstandingPrincipalAmount_456ca287-ebfa-44a0-857a-bc096782dd53" xlink:href="shc-20250630.xsd#shc_DebtInstrumentRedemptionAsPercentOfOutstandingPrincipalAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_22655bb2-1c72-4782-81d8-4f7aced28cb4" xlink:to="loc_shc_DebtInstrumentRedemptionAsPercentOfOutstandingPrincipalAmount_456ca287-ebfa-44a0-857a-bc096782dd53" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentCarryingAmount_0e82968e-d4af-49d5-a0aa-2945716979ad" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentCarryingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_22655bb2-1c72-4782-81d8-4f7aced28cb4" xlink:to="loc_us-gaap_DebtInstrumentCarryingAmount_0e82968e-d4af-49d5-a0aa-2945716979ad" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCredit_c25079dd-7d73-4368-8fe6-dac92acc1c8f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LineOfCredit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_22655bb2-1c72-4782-81d8-4f7aced28cb4" xlink:to="loc_us-gaap_LineOfCredit_c25079dd-7d73-4368-8fe6-dac92acc1c8f" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_DebtInstrumentBaseAmountForDefault_b52e4f1c-1283-47ac-8633-b5821eafcc01" xlink:href="shc-20250630.xsd#shc_DebtInstrumentBaseAmountForDefault"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_22655bb2-1c72-4782-81d8-4f7aced28cb4" xlink:to="loc_shc_DebtInstrumentBaseAmountForDefault_b52e4f1c-1283-47ac-8633-b5821eafcc01" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_DebtInstrumentBasisSpreadAdjustmentOnVariableRate_8132c216-57e3-4873-87c0-f200d9e21f73" xlink:href="shc-20250630.xsd#shc_DebtInstrumentBasisSpreadAdjustmentOnVariableRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_22655bb2-1c72-4782-81d8-4f7aced28cb4" xlink:to="loc_shc_DebtInstrumentBasisSpreadAdjustmentOnVariableRate_8132c216-57e3-4873-87c0-f200d9e21f73" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_DebtInstrumentTriggeringPeriodForDefault_a6fddfa1-9a99-4120-bab8-2b790ebcd789" xlink:href="shc-20250630.xsd#shc_DebtInstrumentTriggeringPeriodForDefault"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_22655bb2-1c72-4782-81d8-4f7aced28cb4" xlink:to="loc_shc_DebtInstrumentTriggeringPeriodForDefault_a6fddfa1-9a99-4120-bab8-2b790ebcd789" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LettersOfCreditOutstandingAmount_931217be-5550-43a2-887a-3ef23566a9ca" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LettersOfCreditOutstandingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_22655bb2-1c72-4782-81d8-4f7aced28cb4" xlink:to="loc_us-gaap_LettersOfCreditOutstandingAmount_931217be-5550-43a2-887a-3ef23566a9ca" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentUnusedBorrowingCapacityAmount_476f4ee3-5157-4589-8b28-5db4ef62f2bc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentUnusedBorrowingCapacityAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_22655bb2-1c72-4782-81d8-4f7aced28cb4" xlink:to="loc_us-gaap_DebtInstrumentUnusedBorrowingCapacityAmount_476f4ee3-5157-4589-8b28-5db4ef62f2bc" xlink:type="arc" order="20"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://soterahealth.com/role/EmployeeBenefitsScheduleofNetBenefitCostsDetails" xlink:type="simple" xlink:href="shc-20250630.xsd#EmployeeBenefitsScheduleofNetBenefitCostsDetails"/>
  <link:definitionLink xlink:role="http://soterahealth.com/role/EmployeeBenefitsScheduleofNetBenefitCostsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_42ccdaa4-4aaa-4014-9961-c9c598ab2090" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DefinedBenefitPlanDisclosureLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_a11fae63-3b81-425f-a807-cecd4ed698a3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_42ccdaa4-4aaa-4014-9961-c9c598ab2090" xlink:to="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_a11fae63-3b81-425f-a807-cecd4ed698a3" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetirementPlanTypeAxis_23176c96-e73e-4fd2-aca8-3e362635ee8a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RetirementPlanTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_a11fae63-3b81-425f-a807-cecd4ed698a3" xlink:to="loc_us-gaap_RetirementPlanTypeAxis_23176c96-e73e-4fd2-aca8-3e362635ee8a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetirementPlanTypeDomain_23176c96-e73e-4fd2-aca8-3e362635ee8a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RetirementPlanTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RetirementPlanTypeAxis_23176c96-e73e-4fd2-aca8-3e362635ee8a" xlink:to="loc_us-gaap_RetirementPlanTypeDomain_23176c96-e73e-4fd2-aca8-3e362635ee8a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetirementPlanTypeDomain_ef123a36-aa28-4069-83b4-0b1c3d5b26e7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RetirementPlanTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RetirementPlanTypeAxis_23176c96-e73e-4fd2-aca8-3e362635ee8a" xlink:to="loc_us-gaap_RetirementPlanTypeDomain_ef123a36-aa28-4069-83b4-0b1c3d5b26e7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PensionPlansDefinedBenefitMember_d6231d54-6ce6-4af2-a598-0ef494a71f32" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PensionPlansDefinedBenefitMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RetirementPlanTypeDomain_ef123a36-aa28-4069-83b4-0b1c3d5b26e7" xlink:to="loc_us-gaap_PensionPlansDefinedBenefitMember_d6231d54-6ce6-4af2-a598-0ef494a71f32" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember_d10f5424-1efa-4830-ab38-c68ec79a08be" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RetirementPlanTypeDomain_ef123a36-aa28-4069-83b4-0b1c3d5b26e7" xlink:to="loc_us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember_d10f5424-1efa-4830-ab38-c68ec79a08be" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_4bac0f3e-a0f5-4f55-a3d0-b4fbf032b78c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_a11fae63-3b81-425f-a807-cecd4ed698a3" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_4bac0f3e-a0f5-4f55-a3d0-b4fbf032b78c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_4bac0f3e-a0f5-4f55-a3d0-b4fbf032b78c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_4bac0f3e-a0f5-4f55-a3d0-b4fbf032b78c" xlink:to="loc_us-gaap_SegmentDomain_4bac0f3e-a0f5-4f55-a3d0-b4fbf032b78c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_a4831777-fe80-45eb-9901-472a3e567079" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_4bac0f3e-a0f5-4f55-a3d0-b4fbf032b78c" xlink:to="loc_us-gaap_SegmentDomain_a4831777-fe80-45eb-9901-472a3e567079" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_NordionMember_90c0a857-b6f7-4402-bdde-3928c7e2edea" xlink:href="shc-20250630.xsd#shc_NordionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_a4831777-fe80-45eb-9901-472a3e567079" xlink:to="loc_shc_NordionMember_90c0a857-b6f7-4402-bdde-3928c7e2edea" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanServiceCost_43b793df-f4ed-450b-a84c-b1d59dd50f43" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DefinedBenefitPlanServiceCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_42ccdaa4-4aaa-4014-9961-c9c598ab2090" xlink:to="loc_us-gaap_DefinedBenefitPlanServiceCost_43b793df-f4ed-450b-a84c-b1d59dd50f43" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanInterestCost_10c92576-2138-4681-8ed1-43aa3e819cdf" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DefinedBenefitPlanInterestCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_42ccdaa4-4aaa-4014-9961-c9c598ab2090" xlink:to="loc_us-gaap_DefinedBenefitPlanInterestCost_10c92576-2138-4681-8ed1-43aa3e819cdf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanExpectedReturnOnPlanAssets_32463a65-a78c-431f-a7c6-61903f44956b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DefinedBenefitPlanExpectedReturnOnPlanAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_42ccdaa4-4aaa-4014-9961-c9c598ab2090" xlink:to="loc_us-gaap_DefinedBenefitPlanExpectedReturnOnPlanAssets_32463a65-a78c-431f-a7c6-61903f44956b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanAmortizationOfGainsLosses_198f3348-645e-457b-b4fa-bad537065e5d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DefinedBenefitPlanAmortizationOfGainsLosses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_42ccdaa4-4aaa-4014-9961-c9c598ab2090" xlink:to="loc_us-gaap_DefinedBenefitPlanAmortizationOfGainsLosses_198f3348-645e-457b-b4fa-bad537065e5d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanNetPeriodicBenefitCost_ff662480-6895-4377-b340-387e720473cc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DefinedBenefitPlanNetPeriodicBenefitCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_42ccdaa4-4aaa-4014-9961-c9c598ab2090" xlink:to="loc_us-gaap_DefinedBenefitPlanNetPeriodicBenefitCost_ff662480-6895-4377-b340-387e720473cc" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://soterahealth.com/role/EmployeeBenefitsNarrativeDetails" xlink:type="simple" xlink:href="shc-20250630.xsd#EmployeeBenefitsNarrativeDetails"/>
  <link:definitionLink xlink:role="http://soterahealth.com/role/EmployeeBenefitsNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_17088ada-cc78-4184-9801-c60eb2991065" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DefinedBenefitPlanDisclosureLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_4cf3e414-e3ca-48e2-aa25-8a4a3a8eb03a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_17088ada-cc78-4184-9801-c60eb2991065" xlink:to="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_4cf3e414-e3ca-48e2-aa25-8a4a3a8eb03a" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetirementPlanTypeAxis_9ee8b9a0-7255-4c3d-b6a3-3a2eba5465ba" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RetirementPlanTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_4cf3e414-e3ca-48e2-aa25-8a4a3a8eb03a" xlink:to="loc_us-gaap_RetirementPlanTypeAxis_9ee8b9a0-7255-4c3d-b6a3-3a2eba5465ba" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetirementPlanTypeDomain_9ee8b9a0-7255-4c3d-b6a3-3a2eba5465ba_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RetirementPlanTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RetirementPlanTypeAxis_9ee8b9a0-7255-4c3d-b6a3-3a2eba5465ba" xlink:to="loc_us-gaap_RetirementPlanTypeDomain_9ee8b9a0-7255-4c3d-b6a3-3a2eba5465ba_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetirementPlanTypeDomain_278d9644-13f7-4375-a987-caec86a2b7c9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RetirementPlanTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RetirementPlanTypeAxis_9ee8b9a0-7255-4c3d-b6a3-3a2eba5465ba" xlink:to="loc_us-gaap_RetirementPlanTypeDomain_278d9644-13f7-4375-a987-caec86a2b7c9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PensionPlansDefinedBenefitMember_b8029ae4-67af-48d2-b669-e6bdcf0bff1c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PensionPlansDefinedBenefitMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RetirementPlanTypeDomain_278d9644-13f7-4375-a987-caec86a2b7c9" xlink:to="loc_us-gaap_PensionPlansDefinedBenefitMember_b8029ae4-67af-48d2-b669-e6bdcf0bff1c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_5baf85d5-024f-47ec-a733-6c1bce2dc2ff" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_4cf3e414-e3ca-48e2-aa25-8a4a3a8eb03a" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_5baf85d5-024f-47ec-a733-6c1bce2dc2ff" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_5baf85d5-024f-47ec-a733-6c1bce2dc2ff_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_5baf85d5-024f-47ec-a733-6c1bce2dc2ff" xlink:to="loc_us-gaap_SegmentDomain_5baf85d5-024f-47ec-a733-6c1bce2dc2ff_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_4f72af5e-40ac-4bd4-b60d-fe5f197eb409" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_5baf85d5-024f-47ec-a733-6c1bce2dc2ff" xlink:to="loc_us-gaap_SegmentDomain_4f72af5e-40ac-4bd4-b60d-fe5f197eb409" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_NordionMember_223bf3fd-fbed-44f0-bbf2-beedef4052b9" xlink:href="shc-20250630.xsd#shc_NordionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_4f72af5e-40ac-4bd4-b60d-fe5f197eb409" xlink:to="loc_shc_NordionMember_223bf3fd-fbed-44f0-bbf2-beedef4052b9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_1624974b-4d66-4b1a-9eb0-66338f5639f6" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_4cf3e414-e3ca-48e2-aa25-8a4a3a8eb03a" xlink:to="loc_srt_RangeAxis_1624974b-4d66-4b1a-9eb0-66338f5639f6" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_1624974b-4d66-4b1a-9eb0-66338f5639f6_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_1624974b-4d66-4b1a-9eb0-66338f5639f6" xlink:to="loc_srt_RangeMember_1624974b-4d66-4b1a-9eb0-66338f5639f6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_0c33a7ec-d780-442e-bd5c-d9cd26f504bf" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_1624974b-4d66-4b1a-9eb0-66338f5639f6" xlink:to="loc_srt_RangeMember_0c33a7ec-d780-442e-bd5c-d9cd26f504bf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_2b7a4ceb-6482-4afc-a6e0-fad144b3a0e2" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_0c33a7ec-d780-442e-bd5c-d9cd26f504bf" xlink:to="loc_srt_MaximumMember_2b7a4ceb-6482-4afc-a6e0-fad144b3a0e2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_LettersOfCreditSolvencyPaymentAsPercentOfMarketValue_6f449295-1c3d-4f4f-b7ae-9d9d37a19ca2" xlink:href="shc-20250630.xsd#shc_LettersOfCreditSolvencyPaymentAsPercentOfMarketValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_17088ada-cc78-4184-9801-c60eb2991065" xlink:to="loc_shc_LettersOfCreditSolvencyPaymentAsPercentOfMarketValue_6f449295-1c3d-4f4f-b7ae-9d9d37a19ca2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LettersOfCreditOutstandingAmount_4ba4e709-9eb0-4620-bd94-c12bb877357c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LettersOfCreditOutstandingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_17088ada-cc78-4184-9801-c60eb2991065" xlink:to="loc_us-gaap_LettersOfCreditOutstandingAmount_4ba4e709-9eb0-4620-bd94-c12bb877357c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_DefinedBenefitPlanAnnualFundingRequirementsPeriod_2f5b4026-f60a-458c-9fd0-dad31d28c941" xlink:href="shc-20250630.xsd#shc_DefinedBenefitPlanAnnualFundingRequirementsPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_17088ada-cc78-4184-9801-c60eb2991065" xlink:to="loc_shc_DefinedBenefitPlanAnnualFundingRequirementsPeriod_2f5b4026-f60a-458c-9fd0-dad31d28c941" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://soterahealth.com/role/OtherComprehensiveIncomeLossDetails" xlink:type="simple" xlink:href="shc-20250630.xsd#OtherComprehensiveIncomeLossDetails"/>
  <link:definitionLink xlink:role="http://soterahealth.com/role/OtherComprehensiveIncomeLossDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_088ce6a5-287e-4e5d-a3ce-55fbd615357f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_0c3f5533-85d5-49c9-a218-46703020a0ac" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_088ce6a5-287e-4e5d-a3ce-55fbd615357f" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_0c3f5533-85d5-49c9-a218-46703020a0ac" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_d64b8cfa-d627-4c32-981d-33bfaffb6bba" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_0c3f5533-85d5-49c9-a218-46703020a0ac" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_d64b8cfa-d627-4c32-981d-33bfaffb6bba" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_d64b8cfa-d627-4c32-981d-33bfaffb6bba_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_d64b8cfa-d627-4c32-981d-33bfaffb6bba" xlink:to="loc_us-gaap_EquityComponentDomain_d64b8cfa-d627-4c32-981d-33bfaffb6bba_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_788743ef-4dc5-4c49-b0e6-df821dffbe66" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_d64b8cfa-d627-4c32-981d-33bfaffb6bba" xlink:to="loc_us-gaap_EquityComponentDomain_788743ef-4dc5-4c49-b0e6-df821dffbe66" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_50125eb9-04c7-406c-9d77-de5178222f52" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_788743ef-4dc5-4c49-b0e6-df821dffbe66" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_50125eb9-04c7-406c-9d77-de5178222f52" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember_9e9d39c5-8470-4161-b23e-0b06f009f277" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_50125eb9-04c7-406c-9d77-de5178222f52" xlink:to="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember_9e9d39c5-8470-4161-b23e-0b06f009f277" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedTranslationAdjustmentMember_1ff7a6d4-a85d-4dca-8616-086de7391aab" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedTranslationAdjustmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_50125eb9-04c7-406c-9d77-de5178222f52" xlink:to="loc_us-gaap_AccumulatedTranslationAdjustmentMember_1ff7a6d4-a85d-4dca-8616-086de7391aab" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedGainLossNetCashFlowHedgeParentMember_13285b02-8b36-4898-a6a9-2727a11d6607" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedGainLossNetCashFlowHedgeParentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_50125eb9-04c7-406c-9d77-de5178222f52" xlink:to="loc_us-gaap_AccumulatedGainLossNetCashFlowHedgeParentMember_13285b02-8b36-4898-a6a9-2727a11d6607" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_3d92a3ff-66a6-4ad2-a82b-45474500b2dd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AOCIAttributableToParentNetOfTaxRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_088ce6a5-287e-4e5d-a3ce-55fbd615357f" xlink:to="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_3d92a3ff-66a6-4ad2-a82b-45474500b2dd" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_ccfb6f8a-8ff0-4d77-8ea3-9c00deb12149" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_3d92a3ff-66a6-4ad2-a82b-45474500b2dd" xlink:to="loc_us-gaap_StockholdersEquity_ccfb6f8a-8ff0-4d77-8ea3-9c00deb12149" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OciBeforeReclassificationsNetOfTaxAttributableToParent_6003af1a-9b69-4a1b-b8fe-63ac111216bc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OciBeforeReclassificationsNetOfTaxAttributableToParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_3d92a3ff-66a6-4ad2-a82b-45474500b2dd" xlink:to="loc_us-gaap_OciBeforeReclassificationsNetOfTaxAttributableToParent_6003af1a-9b69-4a1b-b8fe-63ac111216bc" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationFromAociCurrentPeriodNetOfTaxAttributableToParent_87bfdaaf-f547-4c16-a091-b99719baa1ef" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ReclassificationFromAociCurrentPeriodNetOfTaxAttributableToParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_3d92a3ff-66a6-4ad2-a82b-45474500b2dd" xlink:to="loc_us-gaap_ReclassificationFromAociCurrentPeriodNetOfTaxAttributableToParent_87bfdaaf-f547-4c16-a091-b99719baa1ef" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_9cd219ff-dfdb-4a44-b564-5f7506800e8f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_3d92a3ff-66a6-4ad2-a82b-45474500b2dd" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_9cd219ff-dfdb-4a44-b564-5f7506800e8f" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_4cefd52e-1577-449b-9c28-43c16c0583c0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockholdersEquity"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://soterahealth.com/role/ShareBasedCompensationNarrativeDetails" xlink:type="simple" xlink:href="shc-20250630.xsd#ShareBasedCompensationNarrativeDetails"/>
  <link:definitionLink xlink:role="http://soterahealth.com/role/ShareBasedCompensationNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_33bb9d60-c507-4169-aa3b-23677f530279" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_383ddb69-2a15-4189-8b03-2d391f593fd4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_33bb9d60-c507-4169-aa3b-23677f530279" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_383ddb69-2a15-4189-8b03-2d391f593fd4" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_5fad6cb2-481d-41b6-9974-239b7ce0cad0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_383ddb69-2a15-4189-8b03-2d391f593fd4" xlink:to="loc_us-gaap_AwardTypeAxis_5fad6cb2-481d-41b6-9974-239b7ce0cad0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_5fad6cb2-481d-41b6-9974-239b7ce0cad0_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_5fad6cb2-481d-41b6-9974-239b7ce0cad0" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_5fad6cb2-481d-41b6-9974-239b7ce0cad0_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_d46d0668-38da-41a3-bef5-b1f061ba41c4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_5fad6cb2-481d-41b6-9974-239b7ce0cad0" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_d46d0668-38da-41a3-bef5-b1f061ba41c4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockMember_ae8b9036-5993-4212-b161-40c834feb930" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RestrictedStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_d46d0668-38da-41a3-bef5-b1f061ba41c4" xlink:to="loc_us-gaap_RestrictedStockMember_ae8b9036-5993-4212-b161-40c834feb930" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockOptionMember_9e3904a1-80d1-4311-a238-de0c813f5d83" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EmployeeStockOptionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_d46d0668-38da-41a3-bef5-b1f061ba41c4" xlink:to="loc_us-gaap_EmployeeStockOptionMember_9e3904a1-80d1-4311-a238-de0c813f5d83" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_7d71f9d5-9e33-4c6b-a578-4640de191c6b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_d46d0668-38da-41a3-bef5-b1f061ba41c4" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_7d71f9d5-9e33-4c6b-a578-4640de191c6b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PerformanceSharesMember_ac033a0c-bc84-420b-92f0-b95486a14218" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PerformanceSharesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_d46d0668-38da-41a3-bef5-b1f061ba41c4" xlink:to="loc_us-gaap_PerformanceSharesMember_ac033a0c-bc84-420b-92f0-b95486a14218" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_a55dc7ce-122c-4796-bfab-157d4e35063d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_383ddb69-2a15-4189-8b03-2d391f593fd4" xlink:to="loc_us-gaap_StatementClassOfStockAxis_a55dc7ce-122c-4796-bfab-157d4e35063d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_a55dc7ce-122c-4796-bfab-157d4e35063d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_a55dc7ce-122c-4796-bfab-157d4e35063d" xlink:to="loc_us-gaap_ClassOfStockDomain_a55dc7ce-122c-4796-bfab-157d4e35063d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_e4074544-a734-4e9b-ac26-7dcd864ea2ed" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_a55dc7ce-122c-4796-bfab-157d4e35063d" xlink:to="loc_us-gaap_ClassOfStockDomain_e4074544-a734-4e9b-ac26-7dcd864ea2ed" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_PreIPOB1Member_f6336503-60b8-46b0-b869-aaacb353c057" xlink:href="shc-20250630.xsd#shc_PreIPOB1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_e4074544-a734-4e9b-ac26-7dcd864ea2ed" xlink:to="loc_shc_PreIPOB1Member_f6336503-60b8-46b0-b869-aaacb353c057" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VestingAxis_405ed0bb-8aee-4992-bf00-ff5c83cb2ec4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_VestingAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_383ddb69-2a15-4189-8b03-2d391f593fd4" xlink:to="loc_us-gaap_VestingAxis_405ed0bb-8aee-4992-bf00-ff5c83cb2ec4" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VestingDomain_405ed0bb-8aee-4992-bf00-ff5c83cb2ec4_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_VestingDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_VestingAxis_405ed0bb-8aee-4992-bf00-ff5c83cb2ec4" xlink:to="loc_us-gaap_VestingDomain_405ed0bb-8aee-4992-bf00-ff5c83cb2ec4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VestingDomain_010409f1-eef3-4504-94e9-624ba758e00a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_VestingDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_VestingAxis_405ed0bb-8aee-4992-bf00-ff5c83cb2ec4" xlink:to="loc_us-gaap_VestingDomain_010409f1-eef3-4504-94e9-624ba758e00a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationAwardTrancheOneMember_8e04c9f8-c6f7-4c81-b922-4e81208c1e87" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationAwardTrancheOneMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VestingDomain_010409f1-eef3-4504-94e9-624ba758e00a" xlink:to="loc_us-gaap_ShareBasedCompensationAwardTrancheOneMember_8e04c9f8-c6f7-4c81-b922-4e81208c1e87" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationAwardTrancheTwoMember_d981402f-832a-4efb-a16a-5302d8c22f92" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationAwardTrancheTwoMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VestingDomain_010409f1-eef3-4504-94e9-624ba758e00a" xlink:to="loc_us-gaap_ShareBasedCompensationAwardTrancheTwoMember_d981402f-832a-4efb-a16a-5302d8c22f92" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationAwardTrancheThreeMember_b4a925d7-cd6f-4a52-b38d-bf454a418f50" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationAwardTrancheThreeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VestingDomain_010409f1-eef3-4504-94e9-624ba758e00a" xlink:to="loc_us-gaap_ShareBasedCompensationAwardTrancheThreeMember_b4a925d7-cd6f-4a52-b38d-bf454a418f50" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_ShareBasedPaymentArrangementTrancheFourMember_79d13f6d-9029-4f5c-b3b2-01026edbebb9" xlink:href="shc-20250630.xsd#shc_ShareBasedPaymentArrangementTrancheFourMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VestingDomain_010409f1-eef3-4504-94e9-624ba758e00a" xlink:to="loc_shc_ShareBasedPaymentArrangementTrancheFourMember_79d13f6d-9029-4f5c-b3b2-01026edbebb9" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_ShareBasedPaymentArrangementTrancheFiveMember_f46eef6c-81f2-47bd-944e-e447a07ed3e5" xlink:href="shc-20250630.xsd#shc_ShareBasedPaymentArrangementTrancheFiveMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VestingDomain_010409f1-eef3-4504-94e9-624ba758e00a" xlink:to="loc_shc_ShareBasedPaymentArrangementTrancheFiveMember_f46eef6c-81f2-47bd-944e-e447a07ed3e5" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_98013981-e990-4fe3-8e4e-e5a927b3b991" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_383ddb69-2a15-4189-8b03-2d391f593fd4" xlink:to="loc_srt_RangeAxis_98013981-e990-4fe3-8e4e-e5a927b3b991" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_98013981-e990-4fe3-8e4e-e5a927b3b991_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_98013981-e990-4fe3-8e4e-e5a927b3b991" xlink:to="loc_srt_RangeMember_98013981-e990-4fe3-8e4e-e5a927b3b991_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_c5c75522-0236-4dd6-a109-9301a826f8fd" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_98013981-e990-4fe3-8e4e-e5a927b3b991" xlink:to="loc_srt_RangeMember_c5c75522-0236-4dd6-a109-9301a826f8fd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_07425d4e-4911-4f1f-b1ff-b4ee27a664f9" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_c5c75522-0236-4dd6-a109-9301a826f8fd" xlink:to="loc_srt_MinimumMember_07425d4e-4911-4f1f-b1ff-b4ee27a664f9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_133043a3-e481-49b0-a541-531afe6fb75a" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_c5c75522-0236-4dd6-a109-9301a826f8fd" xlink:to="loc_srt_MaximumMember_133043a3-e481-49b0-a541-531afe6fb75a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameAxis_c4c5b910-f194-4a30-a4d4-136124fed505" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PlanNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_383ddb69-2a15-4189-8b03-2d391f593fd4" xlink:to="loc_us-gaap_PlanNameAxis_c4c5b910-f194-4a30-a4d4-136124fed505" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_c4c5b910-f194-4a30-a4d4-136124fed505_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PlanNameAxis_c4c5b910-f194-4a30-a4d4-136124fed505" xlink:to="loc_us-gaap_PlanNameDomain_c4c5b910-f194-4a30-a4d4-136124fed505_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_6e3dbd6a-b5e0-45cf-84d3-e43cb4d26a3e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PlanNameAxis_c4c5b910-f194-4a30-a4d4-136124fed505" xlink:to="loc_us-gaap_PlanNameDomain_6e3dbd6a-b5e0-45cf-84d3-e43cb4d26a3e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_A2020OmnibusIncentivePlanMember_0f950cea-3a7d-422f-a9b6-55d0a4bacb6e" xlink:href="shc-20250630.xsd#shc_A2020OmnibusIncentivePlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_6e3dbd6a-b5e0-45cf-84d3-e43cb4d26a3e" xlink:to="loc_shc_A2020OmnibusIncentivePlanMember_0f950cea-3a7d-422f-a9b6-55d0a4bacb6e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_8d3fc275-4ccb-465d-a0f6-f3d3e928b35a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_33bb9d60-c507-4169-aa3b-23677f530279" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_8d3fc275-4ccb-465d-a0f6-f3d3e928b35a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentage_6b5af900-ae58-478a-8872-cbf3f3d1fb59" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_33bb9d60-c507-4169-aa3b-23677f530279" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentage_6b5af900-ae58-478a-8872-cbf3f3d1fb59" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllocatedShareBasedCompensationExpense_510fd6bf-7fb3-4260-9786-ac51f755e2b6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AllocatedShareBasedCompensationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_33bb9d60-c507-4169-aa3b-23677f530279" xlink:to="loc_us-gaap_AllocatedShareBasedCompensationExpense_510fd6bf-7fb3-4260-9786-ac51f755e2b6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod_65476cbf-9f16-44d3-b12b-3fcaee06cdd5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_33bb9d60-c507-4169-aa3b-23677f530279" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod_65476cbf-9f16-44d3-b12b-3fcaee06cdd5" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableInPeriod_3b285982-d209-440b-90b3-34397fdd4a86" xlink:href="shc-20250630.xsd#shc_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_33bb9d60-c507-4169-aa3b-23677f530279" xlink:to="loc_shc_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableInPeriod_3b285982-d209-440b-90b3-34397fdd4a86" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedInPeriod_6b84297e-3d0a-4f63-9bc5-023bdd266773" xlink:href="shc-20250630.xsd#shc_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_33bb9d60-c507-4169-aa3b-23677f530279" xlink:to="loc_shc_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedInPeriod_6b84297e-3d0a-4f63-9bc5-023bdd266773" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://soterahealth.com/role/ShareBasedCompensationScheduleofNonvestedRestrictedStockUnitsActivityDetails" xlink:type="simple" xlink:href="shc-20250630.xsd#ShareBasedCompensationScheduleofNonvestedRestrictedStockUnitsActivityDetails"/>
  <link:definitionLink xlink:role="http://soterahealth.com/role/ShareBasedCompensationScheduleofNonvestedRestrictedStockUnitsActivityDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_c8d3743c-b4f2-426d-b602-358f1275bc65" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_3d3e6b8a-ed4a-42ce-bc78-09c3e893a8b3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_c8d3743c-b4f2-426d-b602-358f1275bc65" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_3d3e6b8a-ed4a-42ce-bc78-09c3e893a8b3" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_3e570346-85e9-46ac-b84b-6034969b4ed5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_3d3e6b8a-ed4a-42ce-bc78-09c3e893a8b3" xlink:to="loc_us-gaap_AwardTypeAxis_3e570346-85e9-46ac-b84b-6034969b4ed5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_3e570346-85e9-46ac-b84b-6034969b4ed5_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_3e570346-85e9-46ac-b84b-6034969b4ed5" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_3e570346-85e9-46ac-b84b-6034969b4ed5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_469f8be4-b16a-45f1-9c4f-b975ee48a07f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_3e570346-85e9-46ac-b84b-6034969b4ed5" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_469f8be4-b16a-45f1-9c4f-b975ee48a07f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockMember_64f11652-db44-4a60-837f-eccaabf1d71e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RestrictedStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_469f8be4-b16a-45f1-9c4f-b975ee48a07f" xlink:to="loc_us-gaap_RestrictedStockMember_64f11652-db44-4a60-837f-eccaabf1d71e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_d8a649d6-3f54-4b69-a5f1-2dc6eae4bbf8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_3d3e6b8a-ed4a-42ce-bc78-09c3e893a8b3" xlink:to="loc_us-gaap_StatementClassOfStockAxis_d8a649d6-3f54-4b69-a5f1-2dc6eae4bbf8" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_d8a649d6-3f54-4b69-a5f1-2dc6eae4bbf8_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_d8a649d6-3f54-4b69-a5f1-2dc6eae4bbf8" xlink:to="loc_us-gaap_ClassOfStockDomain_d8a649d6-3f54-4b69-a5f1-2dc6eae4bbf8_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_54d878ba-7e9d-453f-a8f5-91a42e34afc0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_d8a649d6-3f54-4b69-a5f1-2dc6eae4bbf8" xlink:to="loc_us-gaap_ClassOfStockDomain_54d878ba-7e9d-453f-a8f5-91a42e34afc0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_PreIPOB1Member_87e91794-2767-44f5-b997-feb643285f89" xlink:href="shc-20250630.xsd#shc_PreIPOB1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_54d878ba-7e9d-453f-a8f5-91a42e34afc0" xlink:to="loc_shc_PreIPOB1Member_87e91794-2767-44f5-b997-feb643285f89" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_7b4e8699-7d9d-4206-b80d-58d110ec0f9b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_c8d3743c-b4f2-426d-b602-358f1275bc65" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_7b4e8699-7d9d-4206-b80d-58d110ec0f9b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_6bae2f34-091b-4d01-9814-43f3fae1b613" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_7b4e8699-7d9d-4206-b80d-58d110ec0f9b" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_6bae2f34-091b-4d01-9814-43f3fae1b613" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_805ddcc8-fbab-409f-9746-0c3a006cd9e9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_7b4e8699-7d9d-4206-b80d-58d110ec0f9b" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_805ddcc8-fbab-409f-9746-0c3a006cd9e9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_4c323610-9be7-42b4-b824-85f27225413b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://soterahealth.com/role/ShareBasedCompensationScheduleofStockOptionActivityDetails" xlink:type="simple" xlink:href="shc-20250630.xsd#ShareBasedCompensationScheduleofStockOptionActivityDetails"/>
  <link:definitionLink xlink:role="http://soterahealth.com/role/ShareBasedCompensationScheduleofStockOptionActivityDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_198f3e88-ee3b-42cb-a25f-e6ac4e61f996" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_bf3df3b3-9c8d-4a18-8982-9facce72a071" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_198f3e88-ee3b-42cb-a25f-e6ac4e61f996" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_bf3df3b3-9c8d-4a18-8982-9facce72a071" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_1cfe58ca-a27e-4b0b-b1b7-3d07c4010460" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_bf3df3b3-9c8d-4a18-8982-9facce72a071" xlink:to="loc_us-gaap_AwardTypeAxis_1cfe58ca-a27e-4b0b-b1b7-3d07c4010460" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_1cfe58ca-a27e-4b0b-b1b7-3d07c4010460_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_1cfe58ca-a27e-4b0b-b1b7-3d07c4010460" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_1cfe58ca-a27e-4b0b-b1b7-3d07c4010460_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_f39634dd-6c49-4c11-a02c-8b26b9888ff8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_1cfe58ca-a27e-4b0b-b1b7-3d07c4010460" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_f39634dd-6c49-4c11-a02c-8b26b9888ff8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockOptionMember_79dd2ecf-153f-4414-99ba-f6ded44701f0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EmployeeStockOptionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_f39634dd-6c49-4c11-a02c-8b26b9888ff8" xlink:to="loc_us-gaap_EmployeeStockOptionMember_79dd2ecf-153f-4414-99ba-f6ded44701f0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward_6973e5e0-f386-469b-b63d-06d685eefd3a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_198f3e88-ee3b-42cb-a25f-e6ac4e61f996" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward_6973e5e0-f386-469b-b63d-06d685eefd3a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber_4df3bcec-c97d-485d-b4c1-a68148335e18" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward_6973e5e0-f386-469b-b63d-06d685eefd3a" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber_4df3bcec-c97d-485d-b4c1-a68148335e18" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedOptionsForfeitedNumberOfShares_2f977753-7df1-49a0-9163-8eff18a1b88c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedOptionsForfeitedNumberOfShares"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward_6973e5e0-f386-469b-b63d-06d685eefd3a" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedOptionsForfeitedNumberOfShares_2f977753-7df1-49a0-9163-8eff18a1b88c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber_748ec030-8a8d-44f7-86ae-ef3f3c6f4adb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceRollforward_d87a406e-f2f0-4e48-bc76-0aeae07402bc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceRollforward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_198f3e88-ee3b-42cb-a25f-e6ac4e61f996" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceRollforward_d87a406e-f2f0-4e48-bc76-0aeae07402bc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice_b2bf7040-4572-4ac1-8a30-5457d3bb170f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceRollforward_d87a406e-f2f0-4e48-bc76-0aeae07402bc" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice_b2bf7040-4572-4ac1-8a30-5457d3bb170f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageExercisePrice_612d9fc4-25f7-40e7-8154-d5a3575bda33" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageExercisePrice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceRollforward_d87a406e-f2f0-4e48-bc76-0aeae07402bc" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageExercisePrice_612d9fc4-25f7-40e7-8154-d5a3575bda33" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice_08748f39-cd88-4faf-9678-2828e6c90c3c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://soterahealth.com/role/ShareBasedCompensationScheduleofRestrictedStockActivityDetails" xlink:type="simple" xlink:href="shc-20250630.xsd#ShareBasedCompensationScheduleofRestrictedStockActivityDetails"/>
  <link:definitionLink xlink:role="http://soterahealth.com/role/ShareBasedCompensationScheduleofRestrictedStockActivityDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_0f5aca6b-0c79-46f2-b929-ae223e6793a1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_636b5ede-e89b-4426-a1ac-47463b40306c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_0f5aca6b-0c79-46f2-b929-ae223e6793a1" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_636b5ede-e89b-4426-a1ac-47463b40306c" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_2a10184c-7091-4d02-946b-37dab59bc863" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_636b5ede-e89b-4426-a1ac-47463b40306c" xlink:to="loc_us-gaap_AwardTypeAxis_2a10184c-7091-4d02-946b-37dab59bc863" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_2a10184c-7091-4d02-946b-37dab59bc863_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_2a10184c-7091-4d02-946b-37dab59bc863" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_2a10184c-7091-4d02-946b-37dab59bc863_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_916254e1-171d-4ff1-a10c-275e99c48bcf" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_2a10184c-7091-4d02-946b-37dab59bc863" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_916254e1-171d-4ff1-a10c-275e99c48bcf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_e8085248-41e0-44cd-a1e3-ebfbb69b4d6d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_916254e1-171d-4ff1-a10c-275e99c48bcf" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_e8085248-41e0-44cd-a1e3-ebfbb69b4d6d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_af8e3dfa-f537-4ed5-88ef-3d0fc898f7e4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_0f5aca6b-0c79-46f2-b929-ae223e6793a1" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_af8e3dfa-f537-4ed5-88ef-3d0fc898f7e4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_b9d4f1a3-3173-43f9-825f-7b4cae39a5a4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_af8e3dfa-f537-4ed5-88ef-3d0fc898f7e4" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_b9d4f1a3-3173-43f9-825f-7b4cae39a5a4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_668b2047-a838-46ba-8591-8a0cf8d629f0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_af8e3dfa-f537-4ed5-88ef-3d0fc898f7e4" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_668b2047-a838-46ba-8591-8a0cf8d629f0" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_c8c13945-3c6c-4b34-af51-3fee9fd6ea5a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_af8e3dfa-f537-4ed5-88ef-3d0fc898f7e4" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_c8c13945-3c6c-4b34-af51-3fee9fd6ea5a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_4358b193-e51e-4cbe-beee-31a91f3e410e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_af8e3dfa-f537-4ed5-88ef-3d0fc898f7e4" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_4358b193-e51e-4cbe-beee-31a91f3e410e" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_47dc0aaf-6b0f-41c5-a4f4-3b342e93745d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_6798f636-8722-4b7c-8b25-fd9b36741ec8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_0f5aca6b-0c79-46f2-b929-ae223e6793a1" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_6798f636-8722-4b7c-8b25-fd9b36741ec8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_7d8c2006-763a-44c7-a1bc-c88a609a28d1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_6798f636-8722-4b7c-8b25-fd9b36741ec8" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_7d8c2006-763a-44c7-a1bc-c88a609a28d1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_7ee4a95b-692e-4a0a-b896-65e91a04e72a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_6798f636-8722-4b7c-8b25-fd9b36741ec8" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_7ee4a95b-692e-4a0a-b896-65e91a04e72a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_222b5f43-461a-4d3c-b6ac-bfdd3f0c5b06" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_6798f636-8722-4b7c-8b25-fd9b36741ec8" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_222b5f43-461a-4d3c-b6ac-bfdd3f0c5b06" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_00457491-e64f-4e9c-b9aa-167e0ce77813" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_6798f636-8722-4b7c-8b25-fd9b36741ec8" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_00457491-e64f-4e9c-b9aa-167e0ce77813" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_b70fda36-b6ad-492c-a313-283d1dc55eb1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://soterahealth.com/role/ShareBasedCompensationScheduleofPerformanceSharesActivityDetails" xlink:type="simple" xlink:href="shc-20250630.xsd#ShareBasedCompensationScheduleofPerformanceSharesActivityDetails"/>
  <link:definitionLink xlink:role="http://soterahealth.com/role/ShareBasedCompensationScheduleofPerformanceSharesActivityDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_c9132345-091b-4933-86b5-49fe19b59337" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_8de5e8b0-8ade-4c42-9f22-4904f99cd090" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_c9132345-091b-4933-86b5-49fe19b59337" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_8de5e8b0-8ade-4c42-9f22-4904f99cd090" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_191a63ea-1edc-4c3c-ba02-8b97ab849bcf" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_8de5e8b0-8ade-4c42-9f22-4904f99cd090" xlink:to="loc_us-gaap_AwardTypeAxis_191a63ea-1edc-4c3c-ba02-8b97ab849bcf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_191a63ea-1edc-4c3c-ba02-8b97ab849bcf_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_191a63ea-1edc-4c3c-ba02-8b97ab849bcf" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_191a63ea-1edc-4c3c-ba02-8b97ab849bcf_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_70034ce9-8113-4e3e-994c-b232c7b188fe" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_191a63ea-1edc-4c3c-ba02-8b97ab849bcf" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_70034ce9-8113-4e3e-994c-b232c7b188fe" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PerformanceSharesMember_e6b0cb69-4b77-4d3b-a98f-ce270d0c8be3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PerformanceSharesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_70034ce9-8113-4e3e-994c-b232c7b188fe" xlink:to="loc_us-gaap_PerformanceSharesMember_e6b0cb69-4b77-4d3b-a98f-ce270d0c8be3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_bda49808-b9dd-42ef-85e1-8e3bd4fcb2df" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_c9132345-091b-4933-86b5-49fe19b59337" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_bda49808-b9dd-42ef-85e1-8e3bd4fcb2df" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_20f1bec2-58a4-4569-9d71-af8909eef6ef" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_bda49808-b9dd-42ef-85e1-8e3bd4fcb2df" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_20f1bec2-58a4-4569-9d71-af8909eef6ef" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_a29a43bc-4b33-42a7-94bd-23b0ddc6eaeb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_bda49808-b9dd-42ef-85e1-8e3bd4fcb2df" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_a29a43bc-4b33-42a7-94bd-23b0ddc6eaeb" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_34dc79f4-77dd-452e-a1a0-3051864c3410" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_d79b142a-a2fe-4d19-b2e7-0ee3b4ee39f8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_c9132345-091b-4933-86b5-49fe19b59337" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_d79b142a-a2fe-4d19-b2e7-0ee3b4ee39f8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_5e9491fb-3ef4-4d8a-a58d-4157425d25b9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_d79b142a-a2fe-4d19-b2e7-0ee3b4ee39f8" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_5e9491fb-3ef4-4d8a-a58d-4157425d25b9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_0b128dc0-ecdd-41b3-a42c-ec006eea078b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_d79b142a-a2fe-4d19-b2e7-0ee3b4ee39f8" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_0b128dc0-ecdd-41b3-a42c-ec006eea078b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_aad5f267-136f-4aa6-80ef-33ad6f4ef31b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://soterahealth.com/role/EarningsLossPerShareDetails" xlink:type="simple" xlink:href="shc-20250630.xsd#EarningsLossPerShareDetails"/>
  <link:definitionLink xlink:role="http://soterahealth.com/role/EarningsLossPerShareDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_b5c26466-b35e-47eb-824c-015cdb53c8f5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_1eba3529-169e-480d-a709-6c7b71cbc2da" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_b5c26466-b35e-47eb-824c-015cdb53c8f5" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_1eba3529-169e-480d-a709-6c7b71cbc2da" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_2be1c0b3-28e7-4672-b8de-9f21ae86afe6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_1eba3529-169e-480d-a709-6c7b71cbc2da" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_2be1c0b3-28e7-4672-b8de-9f21ae86afe6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesNameDomain_2be1c0b3-28e7-4672-b8de-9f21ae86afe6_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AntidilutiveSecuritiesNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_2be1c0b3-28e7-4672-b8de-9f21ae86afe6" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_2be1c0b3-28e7-4672-b8de-9f21ae86afe6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesNameDomain_15af9571-9476-4c5c-bdf0-6de14de3e7b5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AntidilutiveSecuritiesNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_2be1c0b3-28e7-4672-b8de-9f21ae86afe6" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_15af9571-9476-4c5c-bdf0-6de14de3e7b5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockOptionMember_c508fe5e-f487-4279-bf7a-0fafad2a934d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EmployeeStockOptionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_15af9571-9476-4c5c-bdf0-6de14de3e7b5" xlink:to="loc_us-gaap_EmployeeStockOptionMember_c508fe5e-f487-4279-bf7a-0fafad2a934d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_60a9cf6a-d765-4d9f-90c3-140424aff742" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_15af9571-9476-4c5c-bdf0-6de14de3e7b5" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_60a9cf6a-d765-4d9f-90c3-140424aff742" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PerformanceSharesMember_4130cc2b-ff53-4a72-b0bc-972bb77a38e0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PerformanceSharesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_15af9571-9476-4c5c-bdf0-6de14de3e7b5" xlink:to="loc_us-gaap_PerformanceSharesMember_4130cc2b-ff53-4a72-b0bc-972bb77a38e0" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_5adc86db-fe41-4bb6-ac8e-959c8251b71c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_b5c26466-b35e-47eb-824c-015cdb53c8f5" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_5adc86db-fe41-4bb6-ac8e-959c8251b71c" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://soterahealth.com/role/CommitmentsandContingenciesDetails" xlink:type="simple" xlink:href="shc-20250630.xsd#CommitmentsandContingenciesDetails"/>
  <link:definitionLink xlink:role="http://soterahealth.com/role/CommitmentsandContingenciesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainContingenciesLineItems_45b82ea9-6781-4850-9198-3c8ff5661363" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GainContingenciesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainContingenciesTable_02bfa6c6-c02a-4a9a-93bb-65001cd3e830" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GainContingenciesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_GainContingenciesLineItems_45b82ea9-6781-4850-9198-3c8ff5661363" xlink:to="loc_us-gaap_GainContingenciesTable_02bfa6c6-c02a-4a9a-93bb-65001cd3e830" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementGeographicalAxis_d827046d-374e-4b40-a385-99675f39d807" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_StatementGeographicalAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_GainContingenciesTable_02bfa6c6-c02a-4a9a-93bb-65001cd3e830" xlink:to="loc_srt_StatementGeographicalAxis_d827046d-374e-4b40-a385-99675f39d807" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_d827046d-374e-4b40-a385-99675f39d807_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_d827046d-374e-4b40-a385-99675f39d807" xlink:to="loc_srt_SegmentGeographicalDomain_d827046d-374e-4b40-a385-99675f39d807_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_9ecc29fc-2106-4b52-8d41-06990ba2eb03" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_d827046d-374e-4b40-a385-99675f39d807" xlink:to="loc_srt_SegmentGeographicalDomain_9ecc29fc-2106-4b52-8d41-06990ba2eb03" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_stpr_CA_eaf4a39c-0fbd-4eea-a7cf-3a17e62ed200" xlink:href="https://xbrl.sec.gov/stpr/2025/stpr-2025.xsd#stpr_CA"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_9ecc29fc-2106-4b52-8d41-06990ba2eb03" xlink:to="loc_stpr_CA_eaf4a39c-0fbd-4eea-a7cf-3a17e62ed200" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_stpr_GA_c554fa3a-4759-4243-881e-22f0b45216e0" xlink:href="https://xbrl.sec.gov/stpr/2025/stpr-2025.xsd#stpr_GA"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_9ecc29fc-2106-4b52-8d41-06990ba2eb03" xlink:to="loc_stpr_GA_c554fa3a-4759-4243-881e-22f0b45216e0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_stpr_IL_0baaa19d-60b7-4af3-bf5d-63710dca6c3c" xlink:href="https://xbrl.sec.gov/stpr/2025/stpr-2025.xsd#stpr_IL"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_9ecc29fc-2106-4b52-8d41-06990ba2eb03" xlink:to="loc_stpr_IL_0baaa19d-60b7-4af3-bf5d-63710dca6c3c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LitigationStatusAxis_beef22e6-256d-4d58-a95e-ffd5d100ec7b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LitigationStatusAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_GainContingenciesTable_02bfa6c6-c02a-4a9a-93bb-65001cd3e830" xlink:to="loc_us-gaap_LitigationStatusAxis_beef22e6-256d-4d58-a95e-ffd5d100ec7b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LitigationStatusDomain_beef22e6-256d-4d58-a95e-ffd5d100ec7b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LitigationStatusDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LitigationStatusAxis_beef22e6-256d-4d58-a95e-ffd5d100ec7b" xlink:to="loc_us-gaap_LitigationStatusDomain_beef22e6-256d-4d58-a95e-ffd5d100ec7b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LitigationStatusDomain_a81885c6-b023-4d83-a960-f7e43b6130c6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LitigationStatusDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LitigationStatusAxis_beef22e6-256d-4d58-a95e-ffd5d100ec7b" xlink:to="loc_us-gaap_LitigationStatusDomain_a81885c6-b023-4d83-a960-f7e43b6130c6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PendingLitigationMember_1577275f-9a25-4974-b05e-dc1ae6a6f71f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PendingLitigationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LitigationStatusDomain_a81885c6-b023-4d83-a960-f7e43b6130c6" xlink:to="loc_us-gaap_PendingLitigationMember_1577275f-9a25-4974-b05e-dc1ae6a6f71f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingenciesByNatureOfContingencyAxis_22524efd-361a-4e13-9a4f-6371adb886ac" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LossContingenciesByNatureOfContingencyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_GainContingenciesTable_02bfa6c6-c02a-4a9a-93bb-65001cd3e830" xlink:to="loc_us-gaap_LossContingenciesByNatureOfContingencyAxis_22524efd-361a-4e13-9a4f-6371adb886ac" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingencyNatureDomain_22524efd-361a-4e13-9a4f-6371adb886ac_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LossContingencyNatureDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LossContingenciesByNatureOfContingencyAxis_22524efd-361a-4e13-9a4f-6371adb886ac" xlink:to="loc_us-gaap_LossContingencyNatureDomain_22524efd-361a-4e13-9a4f-6371adb886ac_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingencyNatureDomain_b81211b6-75dc-4767-9b76-8fd349559bdf" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LossContingencyNatureDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LossContingenciesByNatureOfContingencyAxis_22524efd-361a-4e13-9a4f-6371adb886ac" xlink:to="loc_us-gaap_LossContingencyNatureDomain_b81211b6-75dc-4767-9b76-8fd349559bdf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_PersonalInjuryAndWrongfulDeathMember_a256205c-5f4c-4b34-b0dc-db77828675a8" xlink:href="shc-20250630.xsd#shc_PersonalInjuryAndWrongfulDeathMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingencyNatureDomain_b81211b6-75dc-4767-9b76-8fd349559bdf" xlink:to="loc_shc_PersonalInjuryAndWrongfulDeathMember_a256205c-5f4c-4b34-b0dc-db77828675a8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_PersonalInjuryMember_912d745c-010e-4ba9-b29a-6a475c985143" xlink:href="shc-20250630.xsd#shc_PersonalInjuryMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingencyNatureDomain_b81211b6-75dc-4767-9b76-8fd349559bdf" xlink:to="loc_shc_PersonalInjuryMember_912d745c-010e-4ba9-b29a-6a475c985143" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_PropertyDevaluationMember_5826a6df-f0e3-4714-94b5-2db5c8435320" xlink:href="shc-20250630.xsd#shc_PropertyDevaluationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingencyNatureDomain_b81211b6-75dc-4767-9b76-8fd349559bdf" xlink:to="loc_shc_PropertyDevaluationMember_5826a6df-f0e3-4714-94b5-2db5c8435320" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_LitigationCaseAxis_eb51d2e2-bb04-4821-80c8-c7e0c9b83efd" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_LitigationCaseAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_GainContingenciesTable_02bfa6c6-c02a-4a9a-93bb-65001cd3e830" xlink:to="loc_srt_LitigationCaseAxis_eb51d2e2-bb04-4821-80c8-c7e0c9b83efd" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_LitigationCaseTypeDomain_eb51d2e2-bb04-4821-80c8-c7e0c9b83efd_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_LitigationCaseTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_LitigationCaseAxis_eb51d2e2-bb04-4821-80c8-c7e0c9b83efd" xlink:to="loc_srt_LitigationCaseTypeDomain_eb51d2e2-bb04-4821-80c8-c7e0c9b83efd_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_LitigationCaseTypeDomain_a7a3756d-4d26-4e5c-92d7-ccfc95e3fa83" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_LitigationCaseTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_LitigationCaseAxis_eb51d2e2-bb04-4821-80c8-c7e0c9b83efd" xlink:to="loc_srt_LitigationCaseTypeDomain_a7a3756d-4d26-4e5c-92d7-ccfc95e3fa83" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_AssetTransferCaseMember_7708d5a0-5753-4944-99a5-aa07c400e7fc" xlink:href="shc-20250630.xsd#shc_AssetTransferCaseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_LitigationCaseTypeDomain_a7a3756d-4d26-4e5c-92d7-ccfc95e3fa83" xlink:to="loc_shc_AssetTransferCaseMember_7708d5a0-5753-4944-99a5-aa07c400e7fc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_EthyleneOxideTortLitigationGeorgiaMember_72beeb54-b05e-44ee-827e-bf3802c83b8c" xlink:href="shc-20250630.xsd#shc_EthyleneOxideTortLitigationGeorgiaMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_LitigationCaseTypeDomain_a7a3756d-4d26-4e5c-92d7-ccfc95e3fa83" xlink:to="loc_shc_EthyleneOxideTortLitigationGeorgiaMember_72beeb54-b05e-44ee-827e-bf3802c83b8c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_WillowbrookCasesMember_4f16fbdb-7e0e-4f04-87a3-39cbd405b45c" xlink:href="shc-20250630.xsd#shc_WillowbrookCasesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_LitigationCaseTypeDomain_a7a3756d-4d26-4e5c-92d7-ccfc95e3fa83" xlink:to="loc_shc_WillowbrookCasesMember_4f16fbdb-7e0e-4f04-87a3-39cbd405b45c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_TriggeringEventAxis_93a800d7-5e0f-4d8a-b3c4-74fbad59c72f" xlink:href="shc-20250630.xsd#shc_TriggeringEventAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_GainContingenciesTable_02bfa6c6-c02a-4a9a-93bb-65001cd3e830" xlink:to="loc_shc_TriggeringEventAxis_93a800d7-5e0f-4d8a-b3c4-74fbad59c72f" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_TriggeringEventDomain_93a800d7-5e0f-4d8a-b3c4-74fbad59c72f_default" xlink:href="shc-20250630.xsd#shc_TriggeringEventDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_shc_TriggeringEventAxis_93a800d7-5e0f-4d8a-b3c4-74fbad59c72f" xlink:to="loc_shc_TriggeringEventDomain_93a800d7-5e0f-4d8a-b3c4-74fbad59c72f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_TriggeringEventDomain_8262a48a-e28d-464d-8af2-780a50ef5b7c" xlink:href="shc-20250630.xsd#shc_TriggeringEventDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_shc_TriggeringEventAxis_93a800d7-5e0f-4d8a-b3c4-74fbad59c72f" xlink:to="loc_shc_TriggeringEventDomain_8262a48a-e28d-464d-8af2-780a50ef5b7c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_OtherClaimsMember_1f75aec0-da45-4bf8-a499-07765fcce789" xlink:href="shc-20250630.xsd#shc_OtherClaimsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_shc_TriggeringEventDomain_8262a48a-e28d-464d-8af2-780a50ef5b7c" xlink:to="loc_shc_OtherClaimsMember_1f75aec0-da45-4bf8-a499-07765fcce789" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_EligibleJulyClaimantsMember_d94e0c82-036f-4dce-9594-78fa5fc6d0b3" xlink:href="shc-20250630.xsd#shc_EligibleJulyClaimantsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_shc_TriggeringEventDomain_8262a48a-e28d-464d-8af2-780a50ef5b7c" xlink:to="loc_shc_EligibleJulyClaimantsMember_d94e0c82-036f-4dce-9594-78fa5fc6d0b3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_35db8dc1-e75d-49fb-a0d1-f988ea8f0e3a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubsequentEventTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_GainContingenciesTable_02bfa6c6-c02a-4a9a-93bb-65001cd3e830" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_35db8dc1-e75d-49fb-a0d1-f988ea8f0e3a" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_35db8dc1-e75d-49fb-a0d1-f988ea8f0e3a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_35db8dc1-e75d-49fb-a0d1-f988ea8f0e3a" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_35db8dc1-e75d-49fb-a0d1-f988ea8f0e3a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_6d0594e3-721d-4ea3-9e05-2428b29dcb4d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_35db8dc1-e75d-49fb-a0d1-f988ea8f0e3a" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_6d0594e3-721d-4ea3-9e05-2428b29dcb4d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventMember_da8a64c5-5c0b-4e09-a5c2-ba3c1d47297c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubsequentEventMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_6d0594e3-721d-4ea3-9e05-2428b29dcb4d" xlink:to="loc_us-gaap_SubsequentEventMember_da8a64c5-5c0b-4e09-a5c2-ba3c1d47297c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_NumberOfCasesThatWillProceedToJudicialDetermination_5d8fd283-6d86-4868-9094-678abe6ac00e" xlink:href="shc-20250630.xsd#shc_NumberOfCasesThatWillProceedToJudicialDetermination"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GainContingenciesLineItems_45b82ea9-6781-4850-9198-3c8ff5661363" xlink:to="loc_shc_NumberOfCasesThatWillProceedToJudicialDetermination_5d8fd283-6d86-4868-9094-678abe6ac00e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingencyPendingClaimsNumber_633362ab-ef0f-49ec-82aa-fdecb1f953b6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LossContingencyPendingClaimsNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GainContingenciesLineItems_45b82ea9-6781-4850-9198-3c8ff5661363" xlink:to="loc_us-gaap_LossContingencyPendingClaimsNumber_633362ab-ef0f-49ec-82aa-fdecb1f953b6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_NumberOfCasesIncludingPersonalInjuryAndPropertyClaims_7852e4f2-85f1-4cb8-8402-06e050663bc8" xlink:href="shc-20250630.xsd#shc_NumberOfCasesIncludingPersonalInjuryAndPropertyClaims"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GainContingenciesLineItems_45b82ea9-6781-4850-9198-3c8ff5661363" xlink:to="loc_shc_NumberOfCasesIncludingPersonalInjuryAndPropertyClaims_7852e4f2-85f1-4cb8-8402-06e050663bc8" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingencyNewClaimsFiledNumber_0d7b05c1-aae1-42b8-ae42-81ab8d608d99" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LossContingencyNewClaimsFiledNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GainContingenciesLineItems_45b82ea9-6781-4850-9198-3c8ff5661363" xlink:to="loc_us-gaap_LossContingencyNewClaimsFiledNumber_0d7b05c1-aae1-42b8-ae42-81ab8d608d99" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingencyNumberOfPlaintiffs_8a242880-53c0-41b8-9232-717278415999" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LossContingencyNumberOfPlaintiffs"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GainContingenciesLineItems_45b82ea9-6781-4850-9198-3c8ff5661363" xlink:to="loc_us-gaap_LossContingencyNumberOfPlaintiffs_8a242880-53c0-41b8-9232-717278415999" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_LossContingencyPercentOfEligibleClaimants_1b755880-db6c-46ed-abdc-7e0557522d86" xlink:href="shc-20250630.xsd#shc_LossContingencyPercentOfEligibleClaimants"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GainContingenciesLineItems_45b82ea9-6781-4850-9198-3c8ff5661363" xlink:to="loc_shc_LossContingencyPercentOfEligibleClaimants_1b755880-db6c-46ed-abdc-7e0557522d86" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingencyDamagesSoughtValue_256c9f47-8c34-4b93-8291-0d8a670470e3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LossContingencyDamagesSoughtValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GainContingenciesLineItems_45b82ea9-6781-4850-9198-3c8ff5661363" xlink:to="loc_us-gaap_LossContingencyDamagesSoughtValue_256c9f47-8c34-4b93-8291-0d8a670470e3" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_LossContingencyUndiscountedAmountOfInsuranceRelatedAssessmentLiabilityPerOccurrence_ee4cecec-7efd-4945-928c-4559e7f7df01" xlink:href="shc-20250630.xsd#shc_LossContingencyUndiscountedAmountOfInsuranceRelatedAssessmentLiabilityPerOccurrence"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GainContingenciesLineItems_45b82ea9-6781-4850-9198-3c8ff5661363" xlink:to="loc_shc_LossContingencyUndiscountedAmountOfInsuranceRelatedAssessmentLiabilityPerOccurrence_ee4cecec-7efd-4945-928c-4559e7f7df01" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingencyUndiscountedAmountOfInsuranceRelatedAssessmentLiability_cc028fa7-42a4-4a2e-9365-c273fafe981b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LossContingencyUndiscountedAmountOfInsuranceRelatedAssessmentLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GainContingenciesLineItems_45b82ea9-6781-4850-9198-3c8ff5661363" xlink:to="loc_us-gaap_LossContingencyUndiscountedAmountOfInsuranceRelatedAssessmentLiability_cc028fa7-42a4-4a2e-9365-c273fafe981b" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_GrossSettlementAndDefenseCostsIncurred_4079156e-8bf6-46f8-90b0-e0d539632859" xlink:href="shc-20250630.xsd#shc_GrossSettlementAndDefenseCostsIncurred"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GainContingenciesLineItems_45b82ea9-6781-4850-9198-3c8ff5661363" xlink:to="loc_shc_GrossSettlementAndDefenseCostsIncurred_4079156e-8bf6-46f8-90b0-e0d539632859" xlink:type="arc" order="9"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://soterahealth.com/role/FinancialInstrumentsandFinancialRiskNarrativeDetails" xlink:type="simple" xlink:href="shc-20250630.xsd#FinancialInstrumentsandFinancialRiskNarrativeDetails"/>
  <link:definitionLink xlink:role="http://soterahealth.com/role/FinancialInstrumentsandFinancialRiskNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLineItems_1498f4e0-ec1d-4649-96e2-1a76c555e6e7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeTable_dd4191d6-09a1-4e31-8768-f0646c139133" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativeLineItems_1498f4e0-ec1d-4649-96e2-1a76c555e6e7" xlink:to="loc_us-gaap_DerivativeTable_dd4191d6-09a1-4e31-8768-f0646c139133" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_TriggeringEventAxis_6540a6cd-9b04-4668-8259-77d407d68e85" xlink:href="shc-20250630.xsd#shc_TriggeringEventAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_dd4191d6-09a1-4e31-8768-f0646c139133" xlink:to="loc_shc_TriggeringEventAxis_6540a6cd-9b04-4668-8259-77d407d68e85" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_TriggeringEventDomain_6540a6cd-9b04-4668-8259-77d407d68e85_default" xlink:href="shc-20250630.xsd#shc_TriggeringEventDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_shc_TriggeringEventAxis_6540a6cd-9b04-4668-8259-77d407d68e85" xlink:to="loc_shc_TriggeringEventDomain_6540a6cd-9b04-4668-8259-77d407d68e85_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_TriggeringEventDomain_443de459-9713-405d-9f5e-3fa4305e7796" xlink:href="shc-20250630.xsd#shc_TriggeringEventDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_shc_TriggeringEventAxis_6540a6cd-9b04-4668-8259-77d407d68e85" xlink:to="loc_shc_TriggeringEventDomain_443de459-9713-405d-9f5e-3fa4305e7796" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_EffectiveOnAugust312025Member_6acffb8f-c180-45c2-b2b1-b434819e66d6" xlink:href="shc-20250630.xsd#shc_EffectiveOnAugust312025Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_shc_TriggeringEventDomain_443de459-9713-405d-9f5e-3fa4305e7796" xlink:to="loc_shc_EffectiveOnAugust312025Member_6acffb8f-c180-45c2-b2b1-b434819e66d6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_ForwardStartDateBeginningOnJuly312023Member_fb620a79-af4d-47bb-af3e-0cf792d306db" xlink:href="shc-20250630.xsd#shc_ForwardStartDateBeginningOnJuly312023Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_shc_TriggeringEventDomain_443de459-9713-405d-9f5e-3fa4305e7796" xlink:to="loc_shc_ForwardStartDateBeginningOnJuly312023Member_fb620a79-af4d-47bb-af3e-0cf792d306db" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_6fc03091-9935-4b6c-972b-1e9ef37cdce2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_dd4191d6-09a1-4e31-8768-f0646c139133" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_6fc03091-9935-4b6c-972b-1e9ef37cdce2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_6fc03091-9935-4b6c-972b-1e9ef37cdce2_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_6fc03091-9935-4b6c-972b-1e9ef37cdce2" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_6fc03091-9935-4b6c-972b-1e9ef37cdce2_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_b2e4b365-ff8b-4b58-ae1a-ad76208517a0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_6fc03091-9935-4b6c-972b-1e9ef37cdce2" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_b2e4b365-ff8b-4b58-ae1a-ad76208517a0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateSwapMember_9f1edbaf-90cf-48c1-bad1-f0a7ff2a4113" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestRateSwapMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_b2e4b365-ff8b-4b58-ae1a-ad76208517a0" xlink:to="loc_us-gaap_InterestRateSwapMember_9f1edbaf-90cf-48c1-bad1-f0a7ff2a4113" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateCapMember_5e13cdfa-1ecf-48c1-9a22-06a3eaac5c42" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestRateCapMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_b2e4b365-ff8b-4b58-ae1a-ad76208517a0" xlink:to="loc_us-gaap_InterestRateCapMember_5e13cdfa-1ecf-48c1-9a22-06a3eaac5c42" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationAxis_e47d7a64-971f-4278-bf0f-aece22df316d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingDesignationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_dd4191d6-09a1-4e31-8768-f0646c139133" xlink:to="loc_us-gaap_HedgingDesignationAxis_e47d7a64-971f-4278-bf0f-aece22df316d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_e47d7a64-971f-4278-bf0f-aece22df316d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_HedgingDesignationAxis_e47d7a64-971f-4278-bf0f-aece22df316d" xlink:to="loc_us-gaap_HedgingDesignationDomain_e47d7a64-971f-4278-bf0f-aece22df316d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_b0857f6e-5b4d-4ff9-b135-1d6a8116bc12" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_HedgingDesignationAxis_e47d7a64-971f-4278-bf0f-aece22df316d" xlink:to="loc_us-gaap_HedgingDesignationDomain_b0857f6e-5b4d-4ff9-b135-1d6a8116bc12" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DesignatedAsHedgingInstrumentMember_5b488b83-e965-4f86-9648-beba79ec161c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DesignatedAsHedgingInstrumentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingDesignationDomain_b0857f6e-5b4d-4ff9-b135-1d6a8116bc12" xlink:to="loc_us-gaap_DesignatedAsHedgingInstrumentMember_5b488b83-e965-4f86-9648-beba79ec161c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeNotionalAmount_73ba295a-0f5b-40ea-a3a0-59bc13000073" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeNotionalAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_1498f4e0-ec1d-4649-96e2-1a76c555e6e7" xlink:to="loc_us-gaap_DerivativeNotionalAmount_73ba295a-0f5b-40ea-a3a0-59bc13000073" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeNumberOfInstrumentsHeld_9b49e5ac-79b4-4c39-8952-976aa8e2ed3e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeNumberOfInstrumentsHeld"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_1498f4e0-ec1d-4649-96e2-1a76c555e6e7" xlink:to="loc_us-gaap_DerivativeNumberOfInstrumentsHeld_9b49e5ac-79b4-4c39-8952-976aa8e2ed3e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_DerivativeOptionPremium_ab64c816-dfda-4ea6-96a6-635ba18311e5" xlink:href="shc-20250630.xsd#shc_DerivativeOptionPremium"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_1498f4e0-ec1d-4649-96e2-1a76c555e6e7" xlink:to="loc_shc_DerivativeOptionPremium_ab64c816-dfda-4ea6-96a6-635ba18311e5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_PercentOfBorrowingLimitationDueToCashFlowExposure_624dfe14-d631-4f44-8b89-106628570785" xlink:href="shc-20250630.xsd#shc_PercentOfBorrowingLimitationDueToCashFlowExposure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_1498f4e0-ec1d-4649-96e2-1a76c555e6e7" xlink:to="loc_shc_PercentOfBorrowingLimitationDueToCashFlowExposure_624dfe14-d631-4f44-8b89-106628570785" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTax_9268ce1b-674b-482c-bf12-c591c2f3563d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_1498f4e0-ec1d-4649-96e2-1a76c555e6e7" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTax_9268ce1b-674b-482c-bf12-c591c2f3563d" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllowanceForDoubtfulAccountsReceivableCurrent_8cca96e1-6d80-4f96-8360-01fb9ff66c6d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AllowanceForDoubtfulAccountsReceivableCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_1498f4e0-ec1d-4649-96e2-1a76c555e6e7" xlink:to="loc_us-gaap_AllowanceForDoubtfulAccountsReceivableCurrent_8cca96e1-6d80-4f96-8360-01fb9ff66c6d" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://soterahealth.com/role/FinancialInstrumentsandFinancialRiskScheduleofDerivativeInstrumentsDetails" xlink:type="simple" xlink:href="shc-20250630.xsd#FinancialInstrumentsandFinancialRiskScheduleofDerivativeInstrumentsDetails"/>
  <link:definitionLink xlink:role="http://soterahealth.com/role/FinancialInstrumentsandFinancialRiskScheduleofDerivativeInstrumentsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLineItems_d663c267-accd-480c-ab4f-cd3bbcdbc932" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeTable_572703ac-50ae-4146-b899-a8bba158d4d9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativeLineItems_d663c267-accd-480c-ab4f-cd3bbcdbc932" xlink:to="loc_us-gaap_DerivativeTable_572703ac-50ae-4146-b899-a8bba158d4d9" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationAxis_2ebe2fc9-81aa-4aea-9a54-9d5248c1ffea" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingDesignationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_572703ac-50ae-4146-b899-a8bba158d4d9" xlink:to="loc_us-gaap_HedgingDesignationAxis_2ebe2fc9-81aa-4aea-9a54-9d5248c1ffea" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_2ebe2fc9-81aa-4aea-9a54-9d5248c1ffea_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_HedgingDesignationAxis_2ebe2fc9-81aa-4aea-9a54-9d5248c1ffea" xlink:to="loc_us-gaap_HedgingDesignationDomain_2ebe2fc9-81aa-4aea-9a54-9d5248c1ffea_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_266bc009-c360-4d02-b0c3-47a9e5b2a195" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_HedgingDesignationAxis_2ebe2fc9-81aa-4aea-9a54-9d5248c1ffea" xlink:to="loc_us-gaap_HedgingDesignationDomain_266bc009-c360-4d02-b0c3-47a9e5b2a195" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DesignatedAsHedgingInstrumentMember_d4ef5813-5acb-480b-98f1-01a56912340c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DesignatedAsHedgingInstrumentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingDesignationDomain_266bc009-c360-4d02-b0c3-47a9e5b2a195" xlink:to="loc_us-gaap_DesignatedAsHedgingInstrumentMember_d4ef5813-5acb-480b-98f1-01a56912340c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NondesignatedMember_fad75c44-8a75-48ba-84d2-bc8c90161ac8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NondesignatedMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingDesignationDomain_266bc009-c360-4d02-b0c3-47a9e5b2a195" xlink:to="loc_us-gaap_NondesignatedMember_fad75c44-8a75-48ba-84d2-bc8c90161ac8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_facb2289-a50e-4e08-997e-bf03f23d006e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_572703ac-50ae-4146-b899-a8bba158d4d9" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_facb2289-a50e-4e08-997e-bf03f23d006e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_facb2289-a50e-4e08-997e-bf03f23d006e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_facb2289-a50e-4e08-997e-bf03f23d006e" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_facb2289-a50e-4e08-997e-bf03f23d006e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_e070cfc7-3e9d-4f08-952f-dcbbbdc93925" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_facb2289-a50e-4e08-997e-bf03f23d006e" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_e070cfc7-3e9d-4f08-952f-dcbbbdc93925" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateSwapMember_26b07c0f-49ba-4078-b842-bec55fb1daa0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestRateSwapMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_e070cfc7-3e9d-4f08-952f-dcbbbdc93925" xlink:to="loc_us-gaap_InterestRateSwapMember_26b07c0f-49ba-4078-b842-bec55fb1daa0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignExchangeContractMember_99196d77-bc6e-4408-83c7-441fa62cff36" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ForeignExchangeContractMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_e070cfc7-3e9d-4f08-952f-dcbbbdc93925" xlink:to="loc_us-gaap_ForeignExchangeContractMember_99196d77-bc6e-4408-83c7-441fa62cff36" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmbeddedDerivativeFinancialInstrumentsMember_eb5d1f2b-32f1-44d1-8370-74641e53f087" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EmbeddedDerivativeFinancialInstrumentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_e070cfc7-3e9d-4f08-952f-dcbbbdc93925" xlink:to="loc_us-gaap_EmbeddedDerivativeFinancialInstrumentsMember_eb5d1f2b-32f1-44d1-8370-74641e53f087" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeNotionalAmount_6ac2fed1-5d7c-4ec6-9041-51857e4d0840" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeNotionalAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_d663c267-accd-480c-ab4f-cd3bbcdbc932" xlink:to="loc_us-gaap_DerivativeNotionalAmount_6ac2fed1-5d7c-4ec6-9041-51857e4d0840" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeFairValueOfDerivativeAsset_80877b35-b633-4fba-8a5e-e111269f8d25" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeFairValueOfDerivativeAsset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_d663c267-accd-480c-ab4f-cd3bbcdbc932" xlink:to="loc_us-gaap_DerivativeFairValueOfDerivativeAsset_80877b35-b633-4fba-8a5e-e111269f8d25" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeFairValueOfDerivativeLiability_aa08987e-4b48-4145-9c4f-5b9668c3f457" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeFairValueOfDerivativeLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_d663c267-accd-480c-ab4f-cd3bbcdbc932" xlink:to="loc_us-gaap_DerivativeFairValueOfDerivativeLiability_aa08987e-4b48-4145-9c4f-5b9668c3f457" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://soterahealth.com/role/FinancialInstrumentsandFinancialRiskScheduleofDerivativeInstrumentsGainLossDetails" xlink:type="simple" xlink:href="shc-20250630.xsd#FinancialInstrumentsandFinancialRiskScheduleofDerivativeInstrumentsGainLossDetails"/>
  <link:definitionLink xlink:role="http://soterahealth.com/role/FinancialInstrumentsandFinancialRiskScheduleofDerivativeInstrumentsGainLossDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_9c6796ff-ef19-49ee-8b69-7b21ef1a6599" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeInstrumentsGainLossLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_9f3d1753-cae0-4540-a8ce-d16854e4d607" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_9c6796ff-ef19-49ee-8b69-7b21ef1a6599" xlink:to="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_9f3d1753-cae0-4540-a8ce-d16854e4d607" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_36e96430-d7da-4856-a26f-77f11160c13e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_9f3d1753-cae0-4540-a8ce-d16854e4d607" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_36e96430-d7da-4856-a26f-77f11160c13e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_36e96430-d7da-4856-a26f-77f11160c13e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_36e96430-d7da-4856-a26f-77f11160c13e" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_36e96430-d7da-4856-a26f-77f11160c13e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_e3cba59c-17d3-4bfc-9c71-f3b826346fe0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_36e96430-d7da-4856-a26f-77f11160c13e" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_e3cba59c-17d3-4bfc-9c71-f3b826346fe0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateCapMember_46ab8145-7a30-4c44-a06e-cfb0a97de74c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestRateCapMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_e3cba59c-17d3-4bfc-9c71-f3b826346fe0" xlink:to="loc_us-gaap_InterestRateCapMember_46ab8145-7a30-4c44-a06e-cfb0a97de74c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmbeddedDerivativeFinancialInstrumentsMember_cabc3e4b-a4b4-4834-b90b-bc74356b68de" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EmbeddedDerivativeFinancialInstrumentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_e3cba59c-17d3-4bfc-9c71-f3b826346fe0" xlink:to="loc_us-gaap_EmbeddedDerivativeFinancialInstrumentsMember_cabc3e4b-a4b4-4834-b90b-bc74356b68de" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignExchangeContractMember_d91b6a6b-227f-4299-9089-979ea5a86eb9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ForeignExchangeContractMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_e3cba59c-17d3-4bfc-9c71-f3b826346fe0" xlink:to="loc_us-gaap_ForeignExchangeContractMember_d91b6a6b-227f-4299-9089-979ea5a86eb9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeGainLossOnDerivativeNet_a837b30a-51c7-485a-b53b-eb88c1e2f4c0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeGainLossOnDerivativeNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_9c6796ff-ef19-49ee-8b69-7b21ef1a6599" xlink:to="loc_us-gaap_DerivativeGainLossOnDerivativeNet_a837b30a-51c7-485a-b53b-eb88c1e2f4c0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnrealizedGainLossOnDerivatives_71c49f9a-8ff0-4a4b-89fc-98fb5a25961d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_UnrealizedGainLossOnDerivatives"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_9c6796ff-ef19-49ee-8b69-7b21ef1a6599" xlink:to="loc_us-gaap_UnrealizedGainLossOnDerivatives_71c49f9a-8ff0-4a4b-89fc-98fb5a25961d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignCurrencyTransactionGainLossRealizedAfterTax_986cddc6-4211-458c-ac50-b441693b1356" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ForeignCurrencyTransactionGainLossRealizedAfterTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_9c6796ff-ef19-49ee-8b69-7b21ef1a6599" xlink:to="loc_us-gaap_ForeignCurrencyTransactionGainLossRealizedAfterTax_986cddc6-4211-458c-ac50-b441693b1356" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignCurrencyTransactionGainLossUnrealizedAfterTax_5c8742d4-18b8-4625-8114-62c487d98e2e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ForeignCurrencyTransactionGainLossUnrealizedAfterTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_9c6796ff-ef19-49ee-8b69-7b21ef1a6599" xlink:to="loc_us-gaap_ForeignCurrencyTransactionGainLossUnrealizedAfterTax_5c8742d4-18b8-4625-8114-62c487d98e2e" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://soterahealth.com/role/FinancialInstrumentsandFinancialRiskScheduleofFairValueAssetsandLiabilitiesMeasuredonRecurringBasisDetails" xlink:type="simple" xlink:href="shc-20250630.xsd#FinancialInstrumentsandFinancialRiskScheduleofFairValueAssetsandLiabilitiesMeasuredonRecurringBasisDetails"/>
  <link:definitionLink xlink:role="http://soterahealth.com/role/FinancialInstrumentsandFinancialRiskScheduleofFairValueAssetsandLiabilitiesMeasuredonRecurringBasisDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLineItems_d6727992-2741-4a04-b9f1-9d15391dfcef" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeTable_89771044-b2c4-46d5-981c-8cb7e74f2ca1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativeLineItems_d6727992-2741-4a04-b9f1-9d15391dfcef" xlink:to="loc_us-gaap_DerivativeTable_89771044-b2c4-46d5-981c-8cb7e74f2ca1" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationAxis_f8ed07f2-67e8-4771-8ce6-686dfd612171" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingDesignationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_89771044-b2c4-46d5-981c-8cb7e74f2ca1" xlink:to="loc_us-gaap_HedgingDesignationAxis_f8ed07f2-67e8-4771-8ce6-686dfd612171" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_f8ed07f2-67e8-4771-8ce6-686dfd612171_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_HedgingDesignationAxis_f8ed07f2-67e8-4771-8ce6-686dfd612171" xlink:to="loc_us-gaap_HedgingDesignationDomain_f8ed07f2-67e8-4771-8ce6-686dfd612171_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_33e05a0a-20fc-409e-b639-a17c90be8783" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_HedgingDesignationAxis_f8ed07f2-67e8-4771-8ce6-686dfd612171" xlink:to="loc_us-gaap_HedgingDesignationDomain_33e05a0a-20fc-409e-b639-a17c90be8783" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DesignatedAsHedgingInstrumentMember_b647396e-32e8-4397-abc5-5498856c09f0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DesignatedAsHedgingInstrumentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingDesignationDomain_33e05a0a-20fc-409e-b639-a17c90be8783" xlink:to="loc_us-gaap_DesignatedAsHedgingInstrumentMember_b647396e-32e8-4397-abc5-5498856c09f0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NondesignatedMember_8265ac71-9e26-4931-9d6b-64f87b5832be" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NondesignatedMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingDesignationDomain_33e05a0a-20fc-409e-b639-a17c90be8783" xlink:to="loc_us-gaap_NondesignatedMember_8265ac71-9e26-4931-9d6b-64f87b5832be" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByMeasurementBasisAxis_cd642cdc-a6a4-4c9a-bc81-e86def9fba14" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueByMeasurementBasisAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_89771044-b2c4-46d5-981c-8cb7e74f2ca1" xlink:to="loc_us-gaap_FairValueByMeasurementBasisAxis_cd642cdc-a6a4-4c9a-bc81-e86def9fba14" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_cd642cdc-a6a4-4c9a-bc81-e86def9fba14_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PortionAtFairValueFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementBasisAxis_cd642cdc-a6a4-4c9a-bc81-e86def9fba14" xlink:to="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_cd642cdc-a6a4-4c9a-bc81-e86def9fba14_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueDisclosureItemAmountsDomain_eb46cb08-5b0d-446f-9ee5-1fd577b3c3ec" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueDisclosureItemAmountsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementBasisAxis_cd642cdc-a6a4-4c9a-bc81-e86def9fba14" xlink:to="loc_us-gaap_FairValueDisclosureItemAmountsDomain_eb46cb08-5b0d-446f-9ee5-1fd577b3c3ec" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_1b531ca4-ef7b-432a-9094-f96cd15b114c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PortionAtFairValueFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueDisclosureItemAmountsDomain_eb46cb08-5b0d-446f-9ee5-1fd577b3c3ec" xlink:to="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_1b531ca4-ef7b-432a-9094-f96cd15b114c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CarryingReportedAmountFairValueDisclosureMember_e3a8f8a5-5915-407c-8e0d-9d5cb8f7d320" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CarryingReportedAmountFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_1b531ca4-ef7b-432a-9094-f96cd15b114c" xlink:to="loc_us-gaap_CarryingReportedAmountFairValueDisclosureMember_e3a8f8a5-5915-407c-8e0d-9d5cb8f7d320" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_b22fb128-c86e-4257-b35d-de0d6829f5d7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_89771044-b2c4-46d5-981c-8cb7e74f2ca1" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_b22fb128-c86e-4257-b35d-de0d6829f5d7" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_b22fb128-c86e-4257-b35d-de0d6829f5d7_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_b22fb128-c86e-4257-b35d-de0d6829f5d7" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_b22fb128-c86e-4257-b35d-de0d6829f5d7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_13eb88b6-d0d4-485e-95b8-d6540569d622" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_b22fb128-c86e-4257-b35d-de0d6829f5d7" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_13eb88b6-d0d4-485e-95b8-d6540569d622" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateSwapMember_0c18ebf3-2ff4-46a1-9a91-169f1bf5c28c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestRateSwapMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_13eb88b6-d0d4-485e-95b8-d6540569d622" xlink:to="loc_us-gaap_InterestRateSwapMember_0c18ebf3-2ff4-46a1-9a91-169f1bf5c28c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignExchangeForwardMember_78d1d36d-03bf-459a-a1be-32ad3f28fc18" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ForeignExchangeForwardMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_13eb88b6-d0d4-485e-95b8-d6540569d622" xlink:to="loc_us-gaap_ForeignExchangeForwardMember_78d1d36d-03bf-459a-a1be-32ad3f28fc18" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmbeddedDerivativeFinancialInstrumentsMember_90f5406e-7b16-4b21-bdff-5a980b2c4624" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EmbeddedDerivativeFinancialInstrumentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_13eb88b6-d0d4-485e-95b8-d6540569d622" xlink:to="loc_us-gaap_EmbeddedDerivativeFinancialInstrumentsMember_90f5406e-7b16-4b21-bdff-5a980b2c4624" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_d9e9b202-b930-47c3-8a66-c6401fb46f27" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_89771044-b2c4-46d5-981c-8cb7e74f2ca1" xlink:to="loc_us-gaap_DebtInstrumentAxis_d9e9b202-b930-47c3-8a66-c6401fb46f27" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_d9e9b202-b930-47c3-8a66-c6401fb46f27_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_d9e9b202-b930-47c3-8a66-c6401fb46f27" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_d9e9b202-b930-47c3-8a66-c6401fb46f27_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_da107597-eb52-4cef-a055-f5ada881e941" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_d9e9b202-b930-47c3-8a66-c6401fb46f27" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_da107597-eb52-4cef-a055-f5ada881e941" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_TermLoanDue2031Member_8c42e0a7-9e2f-4ac8-917e-c6f9277fba57" xlink:href="shc-20250630.xsd#shc_TermLoanDue2031Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_da107597-eb52-4cef-a055-f5ada881e941" xlink:to="loc_shc_TermLoanDue2031Member_8c42e0a7-9e2f-4ac8-917e-c6f9277fba57" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_TermLoanBDue2031Member_214fabc6-2929-4161-a79d-882969d71a12" xlink:href="shc-20250630.xsd#shc_TermLoanBDue2031Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_da107597-eb52-4cef-a055-f5ada881e941" xlink:to="loc_shc_TermLoanBDue2031Member_214fabc6-2929-4161-a79d-882969d71a12" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_SeniorSecuredNotesDue2031Member_de86a87e-9fed-440e-9f79-cfb70083db83" xlink:href="shc-20250630.xsd#shc_SeniorSecuredNotesDue2031Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_da107597-eb52-4cef-a055-f5ada881e941" xlink:to="loc_shc_SeniorSecuredNotesDue2031Member_de86a87e-9fed-440e-9f79-cfb70083db83" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_FinanceLeaseLiabilityMember_ba82777b-ca7b-4c9e-bee0-b49860d7cab6" xlink:href="shc-20250630.xsd#shc_FinanceLeaseLiabilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_da107597-eb52-4cef-a055-f5ada881e941" xlink:to="loc_shc_FinanceLeaseLiabilityMember_ba82777b-ca7b-4c9e-bee0-b49860d7cab6" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_bbd5173b-4585-4c9f-8e0f-5fb3b6ee857b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_89771044-b2c4-46d5-981c-8cb7e74f2ca1" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_bbd5173b-4585-4c9f-8e0f-5fb3b6ee857b" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_bbd5173b-4585-4c9f-8e0f-5fb3b6ee857b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_bbd5173b-4585-4c9f-8e0f-5fb3b6ee857b" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_bbd5173b-4585-4c9f-8e0f-5fb3b6ee857b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_a64b82d0-8f83-4907-927c-1ef537f77791" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_bbd5173b-4585-4c9f-8e0f-5fb3b6ee857b" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_a64b82d0-8f83-4907-927c-1ef537f77791" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel1Member_356a4f61-de3c-431c-bd7a-51125018d8d9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueInputsLevel1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_a64b82d0-8f83-4907-927c-1ef537f77791" xlink:to="loc_us-gaap_FairValueInputsLevel1Member_356a4f61-de3c-431c-bd7a-51125018d8d9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_cdf21d8a-fce1-47e8-94c4-72d8f5b698b9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueInputsLevel2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_a64b82d0-8f83-4907-927c-1ef537f77791" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_cdf21d8a-fce1-47e8-94c4-72d8f5b698b9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_d07f1eaf-d754-4932-abca-860df89e66b4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueInputsLevel3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_a64b82d0-8f83-4907-927c-1ef537f77791" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_d07f1eaf-d754-4932-abca-860df89e66b4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeFairValueOfDerivativeAsset_ed594a61-0e4c-4a03-8f49-4f79c67e55ae" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeFairValueOfDerivativeAsset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_d6727992-2741-4a04-b9f1-9d15391dfcef" xlink:to="loc_us-gaap_DerivativeFairValueOfDerivativeAsset_ed594a61-0e4c-4a03-8f49-4f79c67e55ae" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeFairValueOfDerivativeLiability_2d3ebb33-8ac0-4cf2-9e1b-3056b571133a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeFairValueOfDerivativeLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_d6727992-2741-4a04-b9f1-9d15391dfcef" xlink:to="loc_us-gaap_DerivativeFairValueOfDerivativeLiability_2d3ebb33-8ac0-4cf2-9e1b-3056b571133a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_LongTermDebtCurrentMaturitiesFairValue_d29870a9-b555-4d8d-a93e-2c26ad820262" xlink:href="shc-20250630.xsd#shc_LongTermDebtCurrentMaturitiesFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_d6727992-2741-4a04-b9f1-9d15391dfcef" xlink:to="loc_shc_LongTermDebtCurrentMaturitiesFairValue_d29870a9-b555-4d8d-a93e-2c26ad820262" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtFairValue_02982d4c-43a9-4ce8-9e77-592cf85d9fe8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongTermDebtFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_d6727992-2741-4a04-b9f1-9d15391dfcef" xlink:to="loc_us-gaap_LongTermDebtFairValue_02982d4c-43a9-4ce8-9e77-592cf85d9fe8" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://soterahealth.com/role/SegmentInformationNarrativeDetails" xlink:type="simple" xlink:href="shc-20250630.xsd#SegmentInformationNarrativeDetails"/>
  <link:definitionLink xlink:role="http://soterahealth.com/role/SegmentInformationNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_de4d0d3c-3132-43f5-9604-bccc97a00dd3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentReportingInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_f9da5e4d-d139-4907-9a42-66fd5e054732" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_de4d0d3c-3132-43f5-9604-bccc97a00dd3" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_f9da5e4d-d139-4907-9a42-66fd5e054732" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsAxis_206456a6-4984-4ae2-abc3-e77559cb1823" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidationItemsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_f9da5e4d-d139-4907-9a42-66fd5e054732" xlink:to="loc_srt_ConsolidationItemsAxis_206456a6-4984-4ae2-abc3-e77559cb1823" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_206456a6-4984-4ae2-abc3-e77559cb1823_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidationItemsAxis_206456a6-4984-4ae2-abc3-e77559cb1823" xlink:to="loc_srt_ConsolidationItemsDomain_206456a6-4984-4ae2-abc3-e77559cb1823_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_c42b6537-f80d-4677-a5f3-aa5e2d66916e" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidationItemsAxis_206456a6-4984-4ae2-abc3-e77559cb1823" xlink:to="loc_srt_ConsolidationItemsDomain_c42b6537-f80d-4677-a5f3-aa5e2d66916e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingSegmentsMember_a979d241-486e-4b5a-9032-ca85c8bd980b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingSegmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_c42b6537-f80d-4677-a5f3-aa5e2d66916e" xlink:to="loc_us-gaap_OperatingSegmentsMember_a979d241-486e-4b5a-9032-ca85c8bd980b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_9e454435-f206-47b4-9569-ee9f26a5887d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_f9da5e4d-d139-4907-9a42-66fd5e054732" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_9e454435-f206-47b4-9569-ee9f26a5887d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_9e454435-f206-47b4-9569-ee9f26a5887d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_9e454435-f206-47b4-9569-ee9f26a5887d" xlink:to="loc_us-gaap_SegmentDomain_9e454435-f206-47b4-9569-ee9f26a5887d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_3245cd58-941c-47ac-9982-48ee6364282b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_9e454435-f206-47b4-9569-ee9f26a5887d" xlink:to="loc_us-gaap_SegmentDomain_3245cd58-941c-47ac-9982-48ee6364282b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_NordionMember_37499e79-63ef-4c5b-8333-7c25962b7966" xlink:href="shc-20250630.xsd#shc_NordionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_3245cd58-941c-47ac-9982-48ee6364282b" xlink:to="loc_shc_NordionMember_37499e79-63ef-4c5b-8333-7c25962b7966" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_8a2b3046-1345-4d86-a2fc-156f829631fb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConcentrationRiskByBenchmarkAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_f9da5e4d-d139-4907-9a42-66fd5e054732" xlink:to="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_8a2b3046-1345-4d86-a2fc-156f829631fb" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_8a2b3046-1345-4d86-a2fc-156f829631fb_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConcentrationRiskBenchmarkDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_8a2b3046-1345-4d86-a2fc-156f829631fb" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_8a2b3046-1345-4d86-a2fc-156f829631fb_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_25644ae6-e8cc-4480-91b3-eebcf3e231eb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConcentrationRiskBenchmarkDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_8a2b3046-1345-4d86-a2fc-156f829631fb" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_25644ae6-e8cc-4480-91b3-eebcf3e231eb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerMember_f8132974-0917-4b07-bccd-9b9b9ebc49fa" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueFromContractWithCustomerMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskBenchmarkDomain_25644ae6-e8cc-4480-91b3-eebcf3e231eb" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerMember_f8132974-0917-4b07-bccd-9b9b9ebc49fa" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskByTypeAxis_f45a27da-b43d-4327-9303-4b6c21d0be3c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConcentrationRiskByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_f9da5e4d-d139-4907-9a42-66fd5e054732" xlink:to="loc_us-gaap_ConcentrationRiskByTypeAxis_f45a27da-b43d-4327-9303-4b6c21d0be3c" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_f45a27da-b43d-4327-9303-4b6c21d0be3c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConcentrationRiskTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_f45a27da-b43d-4327-9303-4b6c21d0be3c" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_f45a27da-b43d-4327-9303-4b6c21d0be3c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_db7ffc5e-c074-4b3d-bdff-c365ce09b708" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConcentrationRiskTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_f45a27da-b43d-4327-9303-4b6c21d0be3c" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_db7ffc5e-c074-4b3d-bdff-c365ce09b708" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CustomerConcentrationRiskMember_31c93be5-39b4-45a1-8f23-106f90b31211" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CustomerConcentrationRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskTypeDomain_db7ffc5e-c074-4b3d-bdff-c365ce09b708" xlink:to="loc_us-gaap_CustomerConcentrationRiskMember_31c93be5-39b4-45a1-8f23-106f90b31211" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MajorCustomersAxis_9b45a674-ae0e-434d-8abb-79d8b49c2b50" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_MajorCustomersAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_f9da5e4d-d139-4907-9a42-66fd5e054732" xlink:to="loc_srt_MajorCustomersAxis_9b45a674-ae0e-434d-8abb-79d8b49c2b50" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_NameOfMajorCustomerDomain_9b45a674-ae0e-434d-8abb-79d8b49c2b50_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_NameOfMajorCustomerDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_MajorCustomersAxis_9b45a674-ae0e-434d-8abb-79d8b49c2b50" xlink:to="loc_srt_NameOfMajorCustomerDomain_9b45a674-ae0e-434d-8abb-79d8b49c2b50_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_NameOfMajorCustomerDomain_a23a7b28-9436-404a-ae99-d6f60adba9a5" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_NameOfMajorCustomerDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_MajorCustomersAxis_9b45a674-ae0e-434d-8abb-79d8b49c2b50" xlink:to="loc_srt_NameOfMajorCustomerDomain_a23a7b28-9436-404a-ae99-d6f60adba9a5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_CustomerOneMember_4c0abec6-859f-40dd-99c2-ec2ecdd8e1bc" xlink:href="shc-20250630.xsd#shc_CustomerOneMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_NameOfMajorCustomerDomain_a23a7b28-9436-404a-ae99-d6f60adba9a5" xlink:to="loc_shc_CustomerOneMember_4c0abec6-859f-40dd-99c2-ec2ecdd8e1bc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_CustomerTwoMember_cc1f680b-e29b-4bfc-8284-5e9ffc32435b" xlink:href="shc-20250630.xsd#shc_CustomerTwoMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_NameOfMajorCustomerDomain_a23a7b28-9436-404a-ae99-d6f60adba9a5" xlink:to="loc_shc_CustomerTwoMember_cc1f680b-e29b-4bfc-8284-5e9ffc32435b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_CustomerThreeMember_c9497038-c260-4215-9890-dc8f029e5a14" xlink:href="shc-20250630.xsd#shc_CustomerThreeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_NameOfMajorCustomerDomain_a23a7b28-9436-404a-ae99-d6f60adba9a5" xlink:to="loc_shc_CustomerThreeMember_c9497038-c260-4215-9890-dc8f029e5a14" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_CustomerFourMember_2fb50644-1f62-4094-85e9-c47340fc665e" xlink:href="shc-20250630.xsd#shc_CustomerFourMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_NameOfMajorCustomerDomain_a23a7b28-9436-404a-ae99-d6f60adba9a5" xlink:to="loc_shc_CustomerFourMember_2fb50644-1f62-4094-85e9-c47340fc665e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NumberOfReportableSegments_5641529b-219e-4996-96f0-8b36f5cd1f79" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NumberOfReportableSegments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_de4d0d3c-3132-43f5-9604-bccc97a00dd3" xlink:to="loc_us-gaap_NumberOfReportableSegments_5641529b-219e-4996-96f0-8b36f5cd1f79" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskPercentage1_e57dc68a-9524-4acc-a8c1-ab91581bc106" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConcentrationRiskPercentage1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_de4d0d3c-3132-43f5-9604-bccc97a00dd3" xlink:to="loc_us-gaap_ConcentrationRiskPercentage1_e57dc68a-9524-4acc-a8c1-ab91581bc106" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://soterahealth.com/role/SegmentInformationScheduleofSegmentReportingInformationbySegmentDetails" xlink:type="simple" xlink:href="shc-20250630.xsd#SegmentInformationScheduleofSegmentReportingInformationbySegmentDetails"/>
  <link:definitionLink xlink:role="http://soterahealth.com/role/SegmentInformationScheduleofSegmentReportingInformationbySegmentDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_1174a91d-f4c6-4823-8837-aab830b22e24" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentReportingInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_04db9374-04f2-4386-90a1-a51b0f931f08" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_1174a91d-f4c6-4823-8837-aab830b22e24" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_04db9374-04f2-4386-90a1-a51b0f931f08" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsAxis_23f055b6-6769-4a63-9b2c-1f51e1a5bb99" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidationItemsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_04db9374-04f2-4386-90a1-a51b0f931f08" xlink:to="loc_srt_ConsolidationItemsAxis_23f055b6-6769-4a63-9b2c-1f51e1a5bb99" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_23f055b6-6769-4a63-9b2c-1f51e1a5bb99_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidationItemsAxis_23f055b6-6769-4a63-9b2c-1f51e1a5bb99" xlink:to="loc_srt_ConsolidationItemsDomain_23f055b6-6769-4a63-9b2c-1f51e1a5bb99_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_8f4f587a-69bd-48be-9cf7-82134b21dd34" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidationItemsAxis_23f055b6-6769-4a63-9b2c-1f51e1a5bb99" xlink:to="loc_srt_ConsolidationItemsDomain_8f4f587a-69bd-48be-9cf7-82134b21dd34" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingSegmentsMember_aa908e9e-1b33-4ff7-8133-c48de3727d2b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingSegmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_8f4f587a-69bd-48be-9cf7-82134b21dd34" xlink:to="loc_us-gaap_OperatingSegmentsMember_aa908e9e-1b33-4ff7-8133-c48de3727d2b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateNonSegmentMember_26a7c062-769d-420e-acd5-92272722d4c7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CorporateNonSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_8f4f587a-69bd-48be-9cf7-82134b21dd34" xlink:to="loc_us-gaap_CorporateNonSegmentMember_26a7c062-769d-420e-acd5-92272722d4c7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IntersegmentEliminationMember_ba177da5-558b-43ba-b3d5-9e10b424072d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IntersegmentEliminationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_8f4f587a-69bd-48be-9cf7-82134b21dd34" xlink:to="loc_us-gaap_IntersegmentEliminationMember_ba177da5-558b-43ba-b3d5-9e10b424072d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_64a35747-aee4-4904-bef6-b1a29dc54861" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_04db9374-04f2-4386-90a1-a51b0f931f08" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_64a35747-aee4-4904-bef6-b1a29dc54861" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_64a35747-aee4-4904-bef6-b1a29dc54861_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_64a35747-aee4-4904-bef6-b1a29dc54861" xlink:to="loc_us-gaap_SegmentDomain_64a35747-aee4-4904-bef6-b1a29dc54861_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_a562d333-7ed4-42a9-b05e-9e140b6bf108" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_64a35747-aee4-4904-bef6-b1a29dc54861" xlink:to="loc_us-gaap_SegmentDomain_a562d333-7ed4-42a9-b05e-9e140b6bf108" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_SterigenicsMember_c9aea512-2a19-4d27-a734-e1724b7c8bc6" xlink:href="shc-20250630.xsd#shc_SterigenicsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_a562d333-7ed4-42a9-b05e-9e140b6bf108" xlink:to="loc_shc_SterigenicsMember_c9aea512-2a19-4d27-a734-e1724b7c8bc6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_NordionMember_d5407bb2-3a10-4e8c-8ada-fb3b1886539d" xlink:href="shc-20250630.xsd#shc_NordionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_a562d333-7ed4-42a9-b05e-9e140b6bf108" xlink:to="loc_shc_NordionMember_d5407bb2-3a10-4e8c-8ada-fb3b1886539d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_NelsonLabsMember_3a0f9c7e-1df7-4b4c-bb51-b59a0bccdb8b" xlink:href="shc-20250630.xsd#shc_NelsonLabsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_a562d333-7ed4-42a9-b05e-9e140b6bf108" xlink:to="loc_shc_NelsonLabsMember_3a0f9c7e-1df7-4b4c-bb51-b59a0bccdb8b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_889367da-8d30-45f6-9cb6-2c443446cfbc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_1174a91d-f4c6-4823-8837-aab830b22e24" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_889367da-8d30-45f6-9cb6-2c443446cfbc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingExpenses_080167bc-c74a-4803-860c-90bd76b8fddb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingExpenses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_1174a91d-f4c6-4823-8837-aab830b22e24" xlink:to="loc_us-gaap_OperatingExpenses_080167bc-c74a-4803-860c-90bd76b8fddb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingIncomeLoss_2f0857e7-79fe-46d0-8f5a-6a6083814d01" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_1174a91d-f4c6-4823-8837-aab830b22e24" xlink:to="loc_us-gaap_OperatingIncomeLoss_2f0857e7-79fe-46d0-8f5a-6a6083814d01" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentExpenditureAdditionToLongLivedAssets_3130972c-6087-4047-8074-ba2bdacf3509" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentExpenditureAdditionToLongLivedAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_1174a91d-f4c6-4823-8837-aab830b22e24" xlink:to="loc_us-gaap_SegmentExpenditureAdditionToLongLivedAssets_3130972c-6087-4047-8074-ba2bdacf3509" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://soterahealth.com/role/SegmentInformationScheduleofReconciliationofOperatingProfitLossfromSegmentstoConsolidatedDetails" xlink:type="simple" xlink:href="shc-20250630.xsd#SegmentInformationScheduleofReconciliationofOperatingProfitLossfromSegmentstoConsolidatedDetails"/>
  <link:definitionLink xlink:role="http://soterahealth.com/role/SegmentInformationScheduleofReconciliationofOperatingProfitLossfromSegmentstoConsolidatedDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_b610faea-3d81-4cd6-b1b5-fed9a132c041" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentReportingInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_51652d78-45cf-4c65-a3d9-a0facfa086b2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_b610faea-3d81-4cd6-b1b5-fed9a132c041" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_51652d78-45cf-4c65-a3d9-a0facfa086b2" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsAxis_c7960b32-10cf-4283-9b25-e9d4d0ef4447" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidationItemsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_51652d78-45cf-4c65-a3d9-a0facfa086b2" xlink:to="loc_srt_ConsolidationItemsAxis_c7960b32-10cf-4283-9b25-e9d4d0ef4447" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_c7960b32-10cf-4283-9b25-e9d4d0ef4447_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidationItemsAxis_c7960b32-10cf-4283-9b25-e9d4d0ef4447" xlink:to="loc_srt_ConsolidationItemsDomain_c7960b32-10cf-4283-9b25-e9d4d0ef4447_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_544b4c62-8002-4a52-893d-02b2495c0c1d" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidationItemsAxis_c7960b32-10cf-4283-9b25-e9d4d0ef4447" xlink:to="loc_srt_ConsolidationItemsDomain_544b4c62-8002-4a52-893d-02b2495c0c1d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingSegmentsMember_898fa1c2-6e19-48a3-aedb-36226014a2dd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingSegmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_544b4c62-8002-4a52-893d-02b2495c0c1d" xlink:to="loc_us-gaap_OperatingSegmentsMember_898fa1c2-6e19-48a3-aedb-36226014a2dd" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MaterialReconcilingItemsMember_840fd7de-41af-423e-b6fe-3bc9ee241b03" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_MaterialReconcilingItemsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_544b4c62-8002-4a52-893d-02b2495c0c1d" xlink:to="loc_us-gaap_MaterialReconcilingItemsMember_840fd7de-41af-423e-b6fe-3bc9ee241b03" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_LitigationCaseAxis_4dcff169-89a8-4b73-90d4-80cf617e0cee" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_LitigationCaseAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_51652d78-45cf-4c65-a3d9-a0facfa086b2" xlink:to="loc_srt_LitigationCaseAxis_4dcff169-89a8-4b73-90d4-80cf617e0cee" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_LitigationCaseTypeDomain_4dcff169-89a8-4b73-90d4-80cf617e0cee_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_LitigationCaseTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_LitigationCaseAxis_4dcff169-89a8-4b73-90d4-80cf617e0cee" xlink:to="loc_srt_LitigationCaseTypeDomain_4dcff169-89a8-4b73-90d4-80cf617e0cee_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_LitigationCaseTypeDomain_b35607e9-411d-4f0f-b9b2-00a2723e9a08" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_LitigationCaseTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_LitigationCaseAxis_4dcff169-89a8-4b73-90d4-80cf617e0cee" xlink:to="loc_srt_LitigationCaseTypeDomain_b35607e9-411d-4f0f-b9b2-00a2723e9a08" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_EthyleneOxideTortLitigationIllinoisMember_9ff6c83e-cf12-4098-8906-f44408922508" xlink:href="shc-20250630.xsd#shc_EthyleneOxideTortLitigationIllinoisMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_LitigationCaseTypeDomain_b35607e9-411d-4f0f-b9b2-00a2723e9a08" xlink:to="loc_shc_EthyleneOxideTortLitigationIllinoisMember_9ff6c83e-cf12-4098-8906-f44408922508" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LitigationStatusAxis_23c0376b-68d6-4920-a938-93ed031aaef7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LitigationStatusAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_51652d78-45cf-4c65-a3d9-a0facfa086b2" xlink:to="loc_us-gaap_LitigationStatusAxis_23c0376b-68d6-4920-a938-93ed031aaef7" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LitigationStatusDomain_23c0376b-68d6-4920-a938-93ed031aaef7_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LitigationStatusDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LitigationStatusAxis_23c0376b-68d6-4920-a938-93ed031aaef7" xlink:to="loc_us-gaap_LitigationStatusDomain_23c0376b-68d6-4920-a938-93ed031aaef7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LitigationStatusDomain_ac06ba84-c29e-4d58-be42-b78b3043d916" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LitigationStatusDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LitigationStatusAxis_23c0376b-68d6-4920-a938-93ed031aaef7" xlink:to="loc_us-gaap_LitigationStatusDomain_ac06ba84-c29e-4d58-be42-b78b3043d916" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PendingLitigationMember_c9dc1ca4-e959-42c3-96e2-8831fc74d7ca" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PendingLitigationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LitigationStatusDomain_ac06ba84-c29e-4d58-be42-b78b3043d916" xlink:to="loc_us-gaap_PendingLitigationMember_c9dc1ca4-e959-42c3-96e2-8831fc74d7ca" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityAxis_7000bfd9-ace8-4e0d-a212-abdf0bd973d2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CreditFacilityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_51652d78-45cf-4c65-a3d9-a0facfa086b2" xlink:to="loc_us-gaap_CreditFacilityAxis_7000bfd9-ace8-4e0d-a212-abdf0bd973d2" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_7000bfd9-ace8-4e0d-a212-abdf0bd973d2_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_7000bfd9-ace8-4e0d-a212-abdf0bd973d2" xlink:to="loc_us-gaap_CreditFacilityDomain_7000bfd9-ace8-4e0d-a212-abdf0bd973d2_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_7b8f31ad-0cfd-45f2-84de-e01411e080fe" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_7000bfd9-ace8-4e0d-a212-abdf0bd973d2" xlink:to="loc_us-gaap_CreditFacilityDomain_7b8f31ad-0cfd-45f2-84de-e01411e080fe" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_d376b686-b9a7-475c-8679-b1cc513d9ff4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevolvingCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_7b8f31ad-0cfd-45f2-84de-e01411e080fe" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_d376b686-b9a7-475c-8679-b1cc513d9ff4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_97efec37-49b3-4b09-bdd1-ed098ba97af9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubsequentEventTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_51652d78-45cf-4c65-a3d9-a0facfa086b2" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_97efec37-49b3-4b09-bdd1-ed098ba97af9" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_97efec37-49b3-4b09-bdd1-ed098ba97af9_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_97efec37-49b3-4b09-bdd1-ed098ba97af9" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_97efec37-49b3-4b09-bdd1-ed098ba97af9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_57bea6e0-3192-4a25-80c5-dcbfa6f461fb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_97efec37-49b3-4b09-bdd1-ed098ba97af9" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_57bea6e0-3192-4a25-80c5-dcbfa6f461fb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventMember_aa5d80af-3b35-40fe-9f29-704dae35155f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubsequentEventMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_57bea6e0-3192-4a25-80c5-dcbfa6f461fb" xlink:to="loc_us-gaap_SubsequentEventMember_aa5d80af-3b35-40fe-9f29-704dae35155f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_SegmentIncomeLoss_0ddfd832-0c3a-418b-a5b6-49203d0f1ecd" xlink:href="shc-20250630.xsd#shc_SegmentIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_b610faea-3d81-4cd6-b1b5-fed9a132c041" xlink:to="loc_shc_SegmentIncomeLoss_0ddfd832-0c3a-418b-a5b6-49203d0f1ecd" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestIncomeExpenseNonoperatingNet_6851942b-7b85-465c-b881-57b7a2010c16" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestIncomeExpenseNonoperatingNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_b610faea-3d81-4cd6-b1b5-fed9a132c041" xlink:to="loc_us-gaap_InterestIncomeExpenseNonoperatingNet_6851942b-7b85-465c-b881-57b7a2010c16" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DepreciationDepletionAndAmortization_066a6181-443f-4c7f-8734-84aa0a406717" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DepreciationDepletionAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_b610faea-3d81-4cd6-b1b5-fed9a132c041" xlink:to="loc_us-gaap_DepreciationDepletionAndAmortization_066a6181-443f-4c7f-8734-84aa0a406717" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllocatedShareBasedCompensationExpense_61c5641b-3438-44a5-bc2f-ed80f8ac9070" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AllocatedShareBasedCompensationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_b610faea-3d81-4cd6-b1b5-fed9a132c041" xlink:to="loc_us-gaap_AllocatedShareBasedCompensationExpense_61c5641b-3438-44a5-bc2f-ed80f8ac9070" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_GainLossOnRefinancingOfDebt_a9bf80c6-699b-4896-b189-cecc70213771" xlink:href="shc-20250630.xsd#shc_GainLossOnRefinancingOfDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_b610faea-3d81-4cd6-b1b5-fed9a132c041" xlink:to="loc_shc_GainLossOnRefinancingOfDebt_a9bf80c6-699b-4896-b189-cecc70213771" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_shc_ForeignCurrencyGainLossAndGainLossOnEmbeddedDerivative_b91417f3-f935-4d73-b04a-8ca5589db58f" xlink:href="shc-20250630.xsd#shc_ForeignCurrencyGainLossAndGainLossOnEmbeddedDerivative"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_b610faea-3d81-4cd6-b1b5-fed9a132c041" xlink:to="loc_shc_ForeignCurrencyGainLossAndGainLossOnEmbeddedDerivative_b91417f3-f935-4d73-b04a-8ca5589db58f" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherRestructuringCosts_f36b25b5-c252-49f0-bc78-92282bef08c5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherRestructuringCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_b610faea-3d81-4cd6-b1b5-fed9a132c041" xlink:to="loc_us-gaap_OtherRestructuringCosts_f36b25b5-c252-49f0-bc78-92282bef08c5" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LitigationSettlementExpense_93ee2aca-72f2-4462-b32f-af8e8dd6445e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LitigationSettlementExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_b610faea-3d81-4cd6-b1b5-fed9a132c041" xlink:to="loc_us-gaap_LitigationSettlementExpense_93ee2aca-72f2-4462-b32f-af8e8dd6445e" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainLossRelatedToLitigationSettlement_0765bc74-9104-4171-be79-16a76aa5596e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GainLossRelatedToLitigationSettlement"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_b610faea-3d81-4cd6-b1b5-fed9a132c041" xlink:to="loc_us-gaap_GainLossRelatedToLitigationSettlement_0765bc74-9104-4171-be79-16a76aa5596e" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetRetirementObligationAccretionExpense_404e1263-a784-4671-95bc-eaa500a629c5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AssetRetirementObligationAccretionExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_b610faea-3d81-4cd6-b1b5-fed9a132c041" xlink:to="loc_us-gaap_AssetRetirementObligationAccretionExpense_404e1263-a784-4671-95bc-eaa500a629c5" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_7102e0b9-d19b-40fb-8dbe-659b60d28fbb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_b610faea-3d81-4cd6-b1b5-fed9a132c041" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_7102e0b9-d19b-40fb-8dbe-659b60d28fbb" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingencyPendingClaimsNumber_846d4198-6af2-4c56-b548-552e36111b23" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LossContingencyPendingClaimsNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_b610faea-3d81-4cd6-b1b5-fed9a132c041" xlink:to="loc_us-gaap_LossContingencyPendingClaimsNumber_846d4198-6af2-4c56-b548-552e36111b23" xlink:type="arc" order="11"/>
  </link:definitionLink>
</link:linkbase>
