(mathematics) A branch of mathematics which deals with spaces and maps between them in abstraction, taking similar theorems from various disparate more concrete branches of mathematics and unifying them.

(category theory) A category whose objects are morphisms (of some given category) with a common codomain, and whose morphisms are commuting triangles where two morphisms of each of such triangles share the said common codomain.

(category theory) A category in which every bimorphism is an isomorphism.

(category theory) A category built out of a pair of functors that have the same codomain.

(category theory) A category whose objects are functors (from some fixed given domain category to some fixed given codomain category) and whose morphisms are natural transformations.

(category theory) The category opposite to that of a slice category.

(information science) A reference that specifies within some taxonomy or text typology one or more defined categories into which the referenced article, computer file etc. belongs.

plural of category reference

(set theory) A fuzzy kind of category in which membership is determined not in binary (true-or-false) fashion but by a more general interval.

(linguistics) Part of speech.