The Radical:

A previous chapter elaborates how to raise a number to a power. The inverse of this operation is known as extracting a root.  For any positive integer n, a number x is the nth root of the number a if it satisfies xⁿ = a.  For example, since 2⁵ = 32, 2 is the fifth root of 32.

To show the nth root of a, the expression a^1/n is frequent used.   The symbol √ is called then radical sign, and the nth root of a could also be shown as ⁿ√ a.  The letter a is the radicand, and n is the index.  The index 2 is commonly omitted for square roots. Example:

√4 = 2

³√27 = 3

⁴√x⁴ = x