High Quality Content by WIKIPEDIA articles! In category theory, a branch of mathematics, a pushout (also called a fibered coproduct or fibered sum or cocartesian square or amalgamed sum) is the colimit of a diagram consisting of two morphisms f : Z X and g : Z Y with a common domain: it is the colimit of the span X leftarrow Z rightarrow Y. Here are some examples of pushouts in familiar categories. Note that in each case, we are only providing a construction of an object in the isomorphism class of pushouts; as mentioned above, there may be other ways to construct it, but they are all equivalent.The pushout is the categorical dual of the pullback.