Actually, every square is a rectangle, since the angles in a square
are always right angles. That's more than saying that a square can be
a rectangle; it is one.
And since squares are rectangles, you know that some rectangles are
squares--namely, the squares are!
We teach children "this is a
rectangle, that is a square. The rectangle's sides are different
lengths". But when you grow up, it's important to think of the square
as a SPECIAL rectangle, because it is all that a rectangle is, and
more.
A square is still a rectangle, but it's not just a rectangle, it's a (pedigreed) square.
In summary, yes a rectangle can be a square.
Hope this helped :)
