In mathematics, a contraction mapping, or contraction, on a metric space M is a function f from M to itself, with the property that there is some real number k < 1 such that, for all x and y in M,
An important property of contraction mappings is given by the Banach fixed point theorem. This states that every contraction mapping on a nonempty complete metric space has a unique fixed point, and that, for any x in M, the sequence x, f (x), f (f (x)), f (f (f (x))), ... converges to the fixed point.