> For the complete documentation index, see [llms.txt](https://docs.snomed.org/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.snomed.org/snomed-ct-practical-guides/snomed-ct-terminology-services-guide/2-terminology-services-overview.md).
# Terminology Services Overview
This chapter defines SNOMED CT terminology services, and it describes the general terminology service categories. Furthermore, it presents three key roles with an interest in SNOMED CT terminology services including end-users and those involved in the procurement of healthcare applications.
## Terminology Services Definition
SNOMED CT terminology services are defined as a set of software functions that interface with and provide effective access to the content and features of one or more SNOMED CT editions.
#### Notes
* Each terminology service is a software function that interfaces with and provides access to information from one or more representations of a terminology.
* The software application that provides *SNOMED CT terminology services* is known as a SNOMED CT terminology server.
* While terminology services may be applicable to several different terminologies, applications that provide *SNOMED CT terminology services,* should support access to the specific design features of SNOMED CT. These include the subtype hierarchy, description logic concept definitions, reference sets and expression constraints.
#### Examples
* Find a concept based on a set of search criteria. The criteria may include text to be matched against terms associated with the concept and constraints requiring a concept to be a subtype of an identified *concept* or a member of an identified reference set.
* Show the preferred term associated with an identified concept.
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