**Defined in theory: Kif-extensions****Source code: kif-extensions.lisp**

**Documentation:**A term is defined if it does not denote the undefined object, called bottom. (defined (F x)) means that the function F is defined for the object x. (F x) denotes its value. In relational terminology, (defined (F x)) means (exists ?y (F x ?y)).

(<=> (Defined ?X) (Not (Undefined ?X)))

- DEFINED is not in the KIF 3.0 spec.