Massachusetts Curriculum Frameworks
5.G.B. Classify two-dimensional figures into categories based on their properties.
5.G.B.3. Understand that attributes belonging to a category of two-dimensional figures also belong to all subcategories of that category. For example, all rectangles have four right angles and squares are rectangles, so all squares have four right angles.
5.G.B.4. Classify two-dimensional figures in a hierarchy based on properties. For example, all rectangles are parallelograms because they are all quadrilaterals with two pairs of opposite sides parallel.