What is a square root?
The square root of a number is the value that, multiplied by itself, gives you the original number. It's the reverse operation of squaring a number.
Example: The square root of 81 = 9, because 9 × 9 = 81.
Practical uses
Calculating the diagonal of a square or rectangle (the Pythagorean theorem relies on square roots), computing standard deviation in statistics, and many physics formulas.
Exponents in general
The square root is a special case of a broader idea: exponents. Squaring means multiplying a number by itself once, cubing means twice, and roots are the reverse operation of all of these.