Natural isomorphism (category theory)

As natural transformations define morphisms between functors, natural isomorphisms define isomorphisms between functors.

Definition

A natural isomorphism is a natural transformation $\eta :F\Rightarrow G$ for which every component ${\eta }_x:Fx\to Gx$ (for some object of $F$'s domain) is an isomorphism.[cite:@riehl2017category]