http://hl7.org/fhir/StructureDefinition/iso21090-PQ-translation|5.2.0

An alternative representation of the same physical quantity expressed in a different unit from a different unit code system and possibly with a different value.
typedestination
baseDefinitionhttp://hl7.org/fhir/StructureDefinition/Extension
typehttp://hl7.org/fhir/StructureDefinition/Extension
Extension.value[x].typehttp://hl7.org/fhir/StructureDefinition/Quantity