Root of unity

In mathematics, a root of unity is an algebraic quantity some power of which is equal to one. An n-th root of unity is a number ζ such that ζn = 1. A primitive n-th root of unity is one which is an n-th root but not an m-th root for any m less than n. Any n-th root of unity is a primitive d-th root of unity for some d dividing n.