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Functor
This article is about the mathematical concept. For other uses, see
Functor (disambiguation)
.
"Functoriality" redirects here. For the Langlands functoriality conjecture in number theory, see
Langlands program § Functoriality
.
Note that contravariant functors reverse the direction of composition.
A functor that maps a category to that same category; e.g.,
polynomial functor
.