functor (plural functors)
- (grammar) a function word
- (computing) a function object
- (category theory) a structure-preserving mapping between categories: if F is a functor from category C to category D, then F maps objects of C to objects of D and morphisms of C to morphisms of D such that any morphism f:X→Y of C is mapped to a morphism F(f): F(X) → F(Y) of D, such that if then , and such that identity morphisms (and only identity morphisms) are mapped to identity morphisms. Note: the functor just described is covariant.
- (in category theory): endofunctor
grammar: function word — see function word
computing: function word — see function object
mathematics: a mapping between categories