- Adjective. (mathematics) That cannot be measured as an integer or fraction; irrational.
- Adjective. Not able to be measured by the same standards as another term in the context; see measurement; contrast with unmeasurable or immeasurable, each of which means not able to be measured at all, the former more generally, the latter generally due to some infinite quality of the thing being described.
- Noun. An incommensurable value or quantity; an irrational number.