**diagram chasing** (*uncountable*)

- (mathematics, somewhat informal) Proof in stages, each of which, in general, depends on the previous stages and can be visualized by means of a diagram of morphisms.
**2016**, Emily Riehl, Category Theory in Context (Aurora: Dover modern math originals)^{[1]}, New York: Dover, →ISBN, OCLC 976394474, page x:- Category theory also contributes new proof techniques, such as
*diagram chasing* or arguments by duality; Steenrod called these methods “abstract nonsense.”^{3} The aim of this text is to introduce the language, philosophy, and basic theorems of category theory. A complementary objective is to put this theory into practice: studying functoriality in algebraic topology, naturality in group theory, and universal properties in algebra.

*To prove the five lemma, just use ***diagram chasing**.

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