The square root of a number, x, is the number that equals x when multiplied by itself.

The square root of 4 is 2, since 2 multiplied by itself equals 4.

en.wikipedia.org/wiki/Square_root

In mathematics, a square root of a number a is a number y such that y<sup>2</sup> = a; in
other words, a number y whose square is a. For example, 4 and −4 are square ...

www.math.com/students/calculators/source/square-root.htm

The Square Root Calculator will find the square root of the number you enter. ...
Related Topic How to calculate square roots without a calculator ...

www.khanacademy.org/math/algebra/rational-exponents-and-radicals/alg1-radicals/v/understanding-square-roots

Learn how square root means what number multiplied by itself will result in the
given number.

www.mathsisfun.com/square-root.html

"Squared" is often written as a little 2 like this: square root of 9 is 3. This says "4
Squared equals 16" (the little 2 says the number appears twice in multiplying) ...

www.khanacademy.org/math/pre-algebra/pre-algebra-exponents-radicals/pre-algebra-square-roots/v/understanding-square-roots

Learn how square root means what number multiplied by itself will result in the
given number.

mathworld.wolfram.com/SquareRoot.html

In common usage, unless otherwise specified, "the" square root is generally
taken to mean the principal square root. The principal square root function sqrt(x)
...

www.squarerootcalculator.co/

Interactive square root calculator that can handle negative, imaginary, and
complex numbers.

www.purplemath.com/modules/radicals.htm

Introduces the square root. Covers basic terminology and demonstrates how to
simplify terms containing square roots.

www.mathwords.com/s/square_root.htm

Square Root. A nonnegative number that must be multiplied times itself to equal
a given number. The square root of x is written or x<sup>½</sup>. For example, since 3<sup>2</sup> = 9.