> 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-international-documents/snomed-ct-glossary/e/extension.md).

# extension

## extension

**This is an abbreviation for SNOMED CT extension.**

## SNOMED CT extension

A set of terminology components and reference set members that add to and are dependent on the SNOMED CT International Edition.

#### Notes

* An *extension* is created, structured, maintained, and distributed in accordance with SNOMED CT specifications and guidelines.
* An *extension* consists of one or more modules. All components and reference set members maintained in an extension include a module identifier that assigns them to a module in that extension.
* *SNOMED CT extensions* may be created and maintained by SNOMED International itself or by SNOMED International Members or Affiliate licensees to which *SNOMED International* has assigned a namespace identifier.
* Components that are created by *Members* or *Affiliates* are identified using SCTIDs that include the namespace identifier assigned to that organization. This ensures that they do not collide with other SCTIDs, and can be traced to an authorized originator. Identifiers of extension *components* and *reference set members* created by *SNOMED International* are not required to include a namespace identifier.
* *Extensions* released by *SNOMED International* contain *components* and *reference set members* that extend, rather than being an essential part of, the SNOMED CT International Edition. However, *SNOMED CT International Extensions* are considered to be part of the overall International Release.
* Members may create, maintain, and distribute *extensions* to address specific national, regional, and language requirements. SNOMED International Affiliates may also create, maintain, and distribute *extensions* to meet the needs of particular software solutions and customers.

## Alternatives

* **Extension**

<a href="https://docs.google.com/forms/d/e/1FAIpQLScTmbZIf0UEQwYDkY27EEWBkaiYkHSbR0_9DmFrMLXoQLyL7Q/viewform?usp=pp_url&#x26;entry.1767247133=SNOMED+Glossary&#x26;entry.670899847=extension" class="button primary">Provide Feedback</a>


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter:

```
GET https://docs.snomed.org/snomed-international-documents/snomed-ct-glossary/e/extension.md?ask=<question>&goal=<endgoal>
```

`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal.

The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.