Metadata that captures the terminological and coding context of health data, including coding system identifiers, version references, and linkages to controlled vocabulary services. It covers terminology systems (SNOMED CT, LOINC, UCUM, EDQM, ICD-10, ATC), format specifications, and conformance requirements. It ensures consistent interpretation of coded clinical data across member states and provides the versioning governance needed to prevent semantic mismatches in cross-border exchange.