> 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/i/intensionally-defined-subset.md).

# intensionally defined subset

## intensionally defined subset

A subset whose membership is defined by an intensional subset definition.

An intensional subset definition is defined as

* A subset definition in which the membership is represented by a set of rules specifying the conditions for inclusion.

#### Notes

* The SNOMED CT expression constraint language is the standard way to represent an *intensional subset definition* of a subset of SNOMED CT concepts.
* A row in a Query Specification Reference Set is the standard way to distribute an *intensional subset definition* of a subset of SNOMED CT concepts.

#### Example

* An example of an intensional subset definition is *concepts that are types of respiratory disease characterized by edema*. This is represented as follows in expression constraint language:\
  < [19829001 |disorder of lung|](http://snomed.info/id/19829001) : [116676008 |associated morphology|](http://snomed.info/id/116676008) = [79654002 |edema|](http://snomed.info/id/79654002)

## Related Links

* Intensionally defined subset
* Extensional subset definition
* Extensionally defined subset
* Practical Guide to Reference Sets
* [Wikipedia comparison of extensional and intensional definitions](https://en.wikipedia.org/wiki/Extensional_and_intensional_definitions)

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