Mac Lane coherence theorem

The Mac Lane coherence theorem is a significant result in category theory, named after the mathematician Saunders Mac Lane. It deals with the coherence of commutative diagrams in the context of monoidal categories, and is closely related to the theory of categories with additional structure, such as monoidal or bicomoidal categories. The coherence theorem states that any two natural isomorphisms between a monoidal category's tensors can be related by a series of coherent transformations.