Is a square a rectangle? (The shape family tree)
A shape hierarchy is a family tree for shapes. Every shape in a group has all the features of the groups above it. A square has 4 right angles, so it is a rectangle, and it has 4 equal sides, so it is a rhombus too.
How you probably learned it
You may have learned shapes as separate categories: squares are squares, and rectangles are rectangles.
How your kid is learning it
Your kid learns that categories overlap. They sort shapes by properties (parallel sides, right angles, equal sides) and use the words always, sometimes, and never. A rectangle is sometimes a square.
Reading the tree
Start at the top: a quadrilateral has 4 straight sides. A parallelogram is a quadrilateral with 2 pairs of parallel sides. A rectangle is a parallelogram with 4 right angles. A rhombus is a parallelogram with 4 equal sides. A square is both.
A note on trapezoids
Schools disagree about trapezoids. Some define a trapezoid as having exactly one pair of parallel sides. Others say at least one, which makes every parallelogram a trapezoid too. Check which definition your kid's class uses.
