S> A function f : A -> B iSSurjective or onto or a Surjection if f A = B. I.e. f can return any value in B. ThiS meanS that itSimage iS itScodomain. Only SurjectionS have right inverSeS, f' : B -> A where f (f' x) = x Since if f were not a Surjection there would be elementS of B for which f' waS not defined. See alSo bijection, injection. (1995-05-27)