(mathematics) A theorem in the elementary theory of numbers: let a and b be integers, not both zero, and let d be their greatest common divisor. Then there exist integers x and y such that ax + by = d.

(genetics) Of corresponding segments of a chromosome in different individuals, identical because they were inherited from a common ancestor without crossover.

(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.

(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.

plural of additive identity

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

plural of identity morphism

plural of identity functor