# defining relationship

## defining relationship

A relationship to a target concept that is always necessarily true for any instance of the source concept.

#### Notes

* All *defining relationships* represent necessary conditions. However, some necessary conditions that can be represented by OWL Axioms cannot be represented by *relationships*.

#### Example

* The *defining relationships* of the concept [53442002 | gastrectomy|](http://snomed.info/id/53442002) include
  * [260686004 | method|](http://snomed.info/id/260686004) = [129304002 | excision - action|](http://snomed.info/id/129304002) and
  * [405813007 | procedure site - Direct|](http://snomed.info/id/405813007) = [69695003 | stomach structure|](http://snomed.info/id/69695003) .

## Alternatives

* **Defining characteristic**

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