A split monomorphismπ:πβπ is a morphism with a postinverse or retractionπ:πβπ, cat
so that πβπ=idπ.
Note that π is necessarily a monomorphism,
and π has the dual property of being a split epimorphism.
Furthermore π need not be unique.
Properties
Let π:πβͺπ be a split monomorphism with retraction π:πβ π