A structured combination of one or more concept identifiers used to express a clinical idea.
- An expression containing a single concept identifier is referred to as a precoordinated expression. An expression that contains two or more concept identifiers is a postcoordinated expression.
- The concept identifiers in a postcoordinated expression are related to one another in accordance with rules expressed in the SNOMED CT Concept Model.
- These rules allow an expression to refine the meaning of a concept by applying more specific values to particular attributes of a more general concept.