> 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/m/mutability.md).

# mutability

## mutability

An indication of whether a release file field value can change between two released versions of the same component or reference set member.

#### Notes

* All released versions of the same component or reference set member have the same id (field), but each version has a different effective time (field).
  * If a field is mutable (Mutable=YES), its value can differ from one version to the next without changing the identifier.
  * If a field is immutable (Mutable=NO), its value must be the same in every version of a component. To change the value associated with an immutable field, the existing component must be inactivated and a new component must be created to replace it. The new component must have a previously unused identifier. The field values are set to replace the inactivated concept with the updated information.
* The mutability for each field, in each type of release file, is indicated in the release file specification table for that component type or reference set.

## Alternatives

* **Mutable**

##

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