Categories in category theory

Category theory is a field of mathematics which deals in an abstract way with mathematical structures and relationships between them. Arising as an abstraction of homological algebra, which itself was affectionately called "abstract nonsense", category theory is sometimes called "generalized abstract nonsense". Categories are the main objects of study in category theory. This Wikipedia category is for articles that define or otherwise deal with one or more specific categories in this mathematical, category-theoretic sense, such as, for example, the category of sets, Set.