Square root, also called quadratic square root, refers to the real number whose multiplication result is equal to [√] for non-negative real numbers, in which the square root belonging to non-negative real numbers is called arithmetic square root. Positive numbers have two square roots; 0 has only one square root, which is 0 itself; Negative numbers have no square root. For example, the square root of 9 is 3 Note: Sometimes the square root we say refers to the arithmetic square root.