In mathematics, a square root of a number "x" is another number that, when multiplied by itself (squared), becomes "x". When it is non-negative, it is represented by the symbol formula_1, and called the principal square root of "x". For example, 2 is the square root of 4, because 2×2=4. Only numbers bigger than or equal to zero have real square roots. The only square root of zero is zero.