Is 1/4 a perfect square?
Yes, it's a perfect square rational number, being equal to
The term 'perfect square' really needs a little context.
We often use it of integers, but it is equally applicable to rational numbers.
In fact, you could say that every non-negative real number is a perfect square in the sense that there is a real number of which it is a square. This is not what people normally mean when they speak of a perfect square though.