surjection

mathematics A function f : A -@# B is surjective or onto or a

surjection if f A = B. I.e. f can return any value in B.

This means that its image is its codomain.

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)