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.
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.
That’s a weird and confusing language if true.
At least in geometry square is a special case of rectangle.
Edit: I looked into dictionary and you are right, it also is another word for right angle. English is a weird language.