Question

Is zero a perfect square?

Answer 1

Virtually all definitions of "perfect square" would include `0`; however, for some reason lists of perfect squares seldom (if ever) include `0`.

Typical definitions are something like
A perfect square is the product of two equal integers;
or
A perfect square is a number whose square root is a rational value.

A bit of consideration should convince you that both of these definitions should include the value `0`.