(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.

(of twins) being the result of two sperm cells fertilizing a single egg, which then splits into two embryos. They share all of the mother's genetic material but only half of the father's.

(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.

(philosophy) The criteria for the persistence of persons over time (i.e what makes one the same person as one was yesterday, or ten years ago), and the criteria for the individuation of persons from others.