The square root of a number n is the number which, when multiplied by itself equals n.
The square root of 9, for example, is 3 because 3 multiplied by 3 = 9.
The square root of 9 is also -3, because -3 multiplied by -3 is also 9.
Not all square roots are whole numbers, and you can't find the square root of a negative number.
Square roots are usually irrational numbers, because they can't be expressed as the quotient of two whole numbers. For example √2 is irrational. However, there are many rational square roots. We've already seen one in the example √9=3 or -3. Another example: √49=7 or -7.