Quadrilateral Thinking Polygons, like living things, can be organized by family, genus, and species. Some members of the quadrilateral class are subclasses of other types of quadrilaterals. Squares, for example, are a subclass of rectangles, because a square is a rectangle whose sides are all the same length. Rectangles, however, are not a subclass of squares, because not all rectangles are squares. One quadrilateral may be a subclass of more than one other kind of quadrilateral.
Squares are a subclass of both rhombuses and rectangles.
But since most rhombuses are not rectangles, and most rectangles are not rhombuses, neither is a subclass of the other. Below, read about a dozen types of quadrilaterals by definition, all have four sides, but each has unique qualities. Then answer the questions on the right. The first is a square and the last is a quadrilateral. The Walt Disney Company.