A retraction of a morphism is a left-inverse: a morphism such that
equals the identity morphism on .
In this case, may also be called a section of , may be called a retract of , and the entire situation is said to split the idempotent
A split monomorphism is a morphism that has a retraction; a split epimorphism is a morphism that is a retraction.
Revised on September 9, 2010 16:52:26
by Toby Bartels