In mathematics, the nth root of a number x is a number r which, when raised to the power of n, equals x
r^n = x,
where n is the degree of the root. A root of degree 2 is called a square root and a root of degree 3, a cube root. Roots of higher degree are referred by using ordinal numbers, as in fourth root, twentieth root, etc.

In calculus, roots are treated as special cases of exponentiation, where the exponent is a fraction: