This article includes a list of general references, but it lacks sufficient corresponding inline citations. Please help to improve this article by introducing more precise citations.(March 2016) (Learn how and when to remove this message)
In mathematics, a comma category (a special case being a slice category) is a construction in category theory. It provides another way of looking at morphisms: instead of simply relating objects of a category to one another, morphisms become objects in their own right. This notion was introduced in 1963 by F. W. Lawvere (Lawvere, 1963 p. 36), although the technique did not[citation needed] become generally known until many years later. Several mathematical concepts can be treated as comma categories. Comma categories also guarantee the existence of some limits and colimits. The name comes from the notation originally used by Lawvere, which involved the comma punctuation mark. The name persists even though standard notation has changed, since the use of a comma as an operator is potentially confusing, and even Lawvere dislikes the uninformative term "comma category" (Lawvere, 1963 p. 13).
In mathematics, a commacategory (a special case being a slice category) is a construction in category theory. It provides another way of looking at morphisms:...
abstractly as initial or terminal objects of a commacategory (see § Connection with commacategories, below). Universal properties occur almost everywhere...
Category theory is a general theory of mathematical structures and their relations that was introduced by Samuel Eilenberg and Saunders Mac Lane in the...
The comma , is a punctuation mark that appears in several variants in different languages. It has the same shape as an apostrophe or single closing quotation...
Applied category theory is an academic discipline in which methods from category theory are used to study other fields including but not limited to computer...
In mathematics, higher category theory is the part of category theory at a higher order, which means that some equalities are replaced by explicit arrows...
In mathematics, a morphism is a concept of category theory that generalizes structure-preserving maps such as homomorphism between algebraic structures...
In mathematics, specifically category theory, a functor is a mapping between categories. Functors were first considered in algebraic topology, where algebraic...
In category theory, the coproduct, or categorical sum, is a construction which includes as examples the disjoint union of sets and of topological spaces...
preserves the identity). (Note that this is precisely the definition of the commacategory of R over the inclusion of unitary rings into rng.) The existence of...
monoidal category Braided monoidal category Topos Category of small categories Semigroupoid Commacategory Localization of a category Enriched category Bicategory...
In category theory, a category is Cartesian closed if, roughly speaking, any morphism defined on a product of two objects can be naturally identified...
In category theory, a branch of mathematics, a functor category D C {\displaystyle D^{C}} is a category where the objects are the functors F : C → D {\displaystyle...
object X to a functor U can be defined as an initial object in the commacategory (X ↓ U). Dually, a universal morphism from U to X is a terminal object...
prototypical example of an abelian category is the category of abelian groups, Ab. Abelian categories are very stable categories; for example they are regular...
specifically in category theory, a preadditive category is another name for an Ab-category, i.e., a category that is enriched over the category of abelian...
maps as morphisms. Another way to think about this category is as the commacategory, ( { ∙ } ↓ {\displaystyle \{\bullet \}\downarrow } Top) where { ∙ }...
In category theory, a branch of mathematics, a closed category is a special kind of category. In a locally small category, the external hom (x, y) maps...
In category theory, a branch of mathematics, a symmetric monoidal category is a monoidal category (i.e. a category in which a "tensor product" ⊗ {\displaystyle...