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EntityQ719395· pop 38· linked from 984 articles

algebraic structure of objects and morphisms between objects, which can be associatively composed if the (co)domains agree

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Encyclopedic overview

This is a category with a collection of objects A, B, C and collection of morphisms denoted f, g, g ∘ f, and the loops are the identity arrows. This category is typically denoted by a boldface 3.

In mathematics, a category (sometimes called an abstract category to distinguish it from a concrete category) is a collection of "objects" that are linked by "arrows". A category has two basic properties: the ability to compose the arrows associatively and the existence of an identity arrow for each object. A simple example is the category of sets, whose objects are sets and whose arrows are functions.

Excerpted from Wikipedia’s “category” article, available under the CC BY-SA 4.0 licence.

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