> 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/s/snomed-ct-extension.md).

# 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**

##

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