A perfect square is a number that can be expressed as the product of two equal integers.
Examples of perfect squares
 9
 9 is a perfect square because it can be expressed as 3 * 3 (the product of two equal integers).
 16
 16 is a perfect square because it can be expressed as 4 * 4 (the product of two equal integers).
 25
 25 is a perfect square because it can be expressed as 5 * 5 (the product of two equal integers).
Non examples of perfect squares
 8

8 is not a perfect square because you cannot express it as the product of two equal integers.
 5

5 is not a perfect square because it cannot be expressed as the product of two equal integers.
 7

7 is not a perfect square because you cannot express it as the product of two equal integers.