The square root of a number is a number that squares (multiplies by itself) to give the number.

Each number (except zero) has two square roots: a positive square root and a negative square root.

For example, \(9 = 3 \times 3\), so \(3\) is a square root of \(9\), but \(9 = (-3) \times (-3)\) as well, so \(-3\) is also a square root of \(9\).

We use the symbol \(\sqrt{\;}\) to stand for the positive square root of a number. If we want to use a symbol for a negative square root of a number, we put a minus sign in front of the \(\sqrt{\;}\) symbol.

For example, \(\sqrt{49} = 7\) (because \(49 = 7 \times 7\)), and \(-\sqrt{49} = -7\).

The square numbers \(4, 9\) and \(16\) in the picture have square roots of \(2, 3\) and \(4\) in that order. Did you notice that these are the numbers of dots along each side of the squares in the picture?