What term is used for an expression description?

The term that accurately represents an expression description is "Annotation." An annotation serves as a note or explanatory comment that clarifies, elucidates, or provides context to the expression it accompanies. This is particularly vital in design and modeling environments like NX, where complex data and expressions are used.

Annotations help in understanding the purpose and form of expressions more easily for anyone interacting with the design, whether for reference, collaboration, or further modifications. They can include descriptions of what an expression does, its significance, or any specific constraints that should be considered.

Comments, while similar, tend to be more informal and are often used for coder's notes or temporary explanations, which may not be intended for end-users. A description can be more general and doesn't specifically imply the contextual clarification needed for expressions, whereas labels typically refer to tags or identifiers associated with objects rather than detailed explanations of expressions.