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Work Group Vocabulary Ballot Status: Informative

The Terminology Module provides an overview and guide to the FHIR resources, operations, coded data types and externally-defined standard and FHIR-defined terminologies that are used for representing and communicating coded, structured data in the FHIR core specification and profiles. Collectively, these capabilities are used to provide the terminology service functionality required for supporting the use of coded data in FHIR resources throughout the specification as described in the other modules.

The terminology resources and their relationships are shown below:

Image showing the terminology resources and relationships

The ElementDefinition type (shown with a dotted box) is described elsewhere in the specification in the Foundation and Conformance modules.

The Terminology Module covers the following:


Terminology Service


  • CodeSystem
  • ValueSet
  • ConceptMap

Coded Data Types


For security considerations for terminology services, see the Terminology Service page Security section. For more general considerations, see the Security and Privacy module.

  • Expand a value set
  • Validate a code
  • Look up a display term for a code
  • Translate a code from one value set to another
  • Maintain a client-side transitive closure table on subsumption relationships
  • Test subsumption between concepts
  • For a set of property/concept pairs, return the set of concepts for the requested properties

The following three terminology resources have been tested and are being used in production tooling, and as such they have reached a maturity level where changes become less likely and are now considered to be normative candidates. We intend to progress these resources through to normative status via the May and September 2018 R4 ballots.

Other terminology resources are still in earlier stages of development. We intend to continue to develop and test these resources and advance them through the Maturity Levels at Connectathons and elsewhere.