I didn’t say rectangles are squares, I said rectangles are square.
Square can be an adjective. When you say a rectangle is square, you’re saying all four corners are square. If you make a picture frame in the shape of a oblique parallelogram, it’s not square. If you make it in the shape of a rectangle, it’s square. If you make it in the shape of a square, it is both square and a square.
It’s the other way. All squares are rectangles, but not all rectangles are squares.
Rect-angle, rectus-angle, right/proper-angle
I didn’t say rectangles are squares, I said rectangles are square.
Square can be an adjective. When you say a rectangle is square, you’re saying all four corners are square. If you make a picture frame in the shape of a oblique parallelogram, it’s not square. If you make it in the shape of a rectangle, it’s square. If you make it in the shape of a square, it is both square and a square.