Source : Free On-Line Dictionary of Computing

bijection
     
         A {function} is bijective or a bijection or a
        one-to-one correspondence if it is both {injective} (no two
        values map to the same value) and {surjective} (for every
        element of the {codomain} there is some element of the
        {domain} which maps to it).  I.e. there is exactly one element
        of the domain which maps to each element of the codomain.
     
        For a general bijection f from the set A to the set B:
     
        f'(f(a)) = a where a is in A and f(f'(b)) = b where b is in B.
     
        A and B could be disjoint sets.
     
        See also {injection}, {surjection}, {isomorphism},
        {permutation}.
     
        (2001-05-10)