Q: If a square is a rectangle, but a rectangle not a square, and a circle is an oval, but a circle not an oval, is a triangle a triangle, but a triangle not a triangle?
A: an equilateral triangle is a triangle but a triangle is not necessarily an equilateral triangle, and i think you also made a mistake in your cirle/oval analogy by listing them in the same order twice, and also, i think all your 'not' clauses probably require to say 'not necessarily' to really get at what i think you're trying to say. indeed a rectangle CAN be a square, if the measurements are equal