In mathematics, a bijection, or a bijective function is a function f from a set X to a set Y with the property that, for every y in Y, there's exactly one x in X such that f(x) = y. Alternatively, f is bijective if it's a one-to-one correspondence between those sets; for example, both one-to-one (injective) and onto (surjective). (One-to-one function means one-to-one correspondence (for example, bijection) to some authors, but injection to others.) For example, consider the function succ, defin… (More on Bijection)