---
type: "fhir-fhirpath-function"
title: "FHIR FHIRPath Function: %terminologies.expand"
source: "source/fhirpath.html"
---

# FHIR FHIRPath Function: %terminologies.expand

This page is part of **FHIR FHIRPath** (FHIR-specific extensions). Base spec lives at [FHIRPath](/fhirpath).

`%terminologies.expand(valueSet, params) : ValueSet`

This calls the [Terminology Service $expand](terminology-service#expand) operation ([formal definition](valueset-operation-expand)).

Parameters:

-   **valueSet**: either an actual [ValueSet](valueset), or a [canonical URL](references#canonical) reference to a value set.
-   **params**: a URL encoded string with other parameters for the expand operation (e.g., 'displayLanguage=en&activeOnly=true')

**Return Value:** a [ValueSet](valueset) with an expansion. If an error occurs, the return value is empty.

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