What qualifies a number as a "perfect square"? List some examples.

A number that is the product of a whole number multiplied by itself.

Step-by-step explanation:

4, 9, 16, 25 are all perfect squares because 2x2=4, 3x3=9, 4x4=16, 5x5=25

A perfect squares is a number whose square root is a natural number. For example 81, 16 have square roots 9 and 4 respectively. Thus these are perfect squares. However we have no natural number for root of 82. Thus 82 is not a perfect square. Its root will be in decimals