(logic) The logical principle that anything equals itself, expressed by the symbolic equation A=A.

(category theory) A unique morphism corresponding to each object of a category, which has its domain equal to its codomain, and which composed with any morphism (with which it is composable) gives that same morphism.

(category theory) A functor from a category to itself which maps each object of that category to itself and each morphism of that category to itself.

(politics) An advocate of or participant in identity politics.

plural of identity morphism

plural of identity functor

(sociology) An identity or feeling of belonging to a group.

plural of identity politician

(UK, law enforcement) A process by which a witness confirms the identity of a criminal suspect, by viewing the suspect together with other people who were not involved in the crime.

(mathematics) Given a binary operation × defined on a set S which also has additive operation + and additive identity 0, the property that a × (b×c) + b × (c×a) + c × (a×b) = 0 for all a, b, c in S.