A function between categories which maps objects to objects and morphisms to morphisms. Functors exist in both covariant and contravariant types.
Functor
See also
Category, Contravariant Functor, Covariant Functor, Eilenberg-Steenrod Axioms, Forgetful Functor, Morphism, Schur Functor, Tensor Product FunctorExplore with Wolfram|Alpha
Cite this as:
Weisstein, Eric W. "Functor." From MathWorld--A Wolfram Resource. https://mathworld.wolfram.com/Functor.html