A square root of a number 'x' is a number y such that y2 = x, in other words, a number y whose square is y. For example, 3 is the square root of 9 because 32 = 3•3 = 9, -3 is square root of 9 because (-3)2 = (-3)•(-3) = 9. When writing math, people often use sqrt(x) to mean the square root of x