If an integer, like 25 has an integer, like 5, that can be multiplied by itself, then the 5 is called a square root and the 25 is called a perfect square.
Since floating point numbers cannot be expressed as the ratio of two integers, they are called irrational. These numbers, not being perfect square, do not have a square root. Now you can approximate, apply rounding rules, etc and guess a "square root". But unless the original number is the ratio of two integers, and a perfect square, this guess is not a square root.
In addition both 0 and negative numbers don't have square roots either.
A good example is trying to find the square root of 2.
