A quadrilateral is any polygon with four sides. The four angles always add up to 360°.
Parallelograms have two pairs of parallel sides. Rectangles are parallelograms with right angles. Rhombuses are parallelograms with all sides equal. Squares are both — right angles AND all sides equal.
Trapezoids have exactly one pair of parallel sides.
The relationships form a family tree: every square is a rectangle and a rhombus, but not every rectangle is a square.
Remember
Quad = four. All quadrilateral angles add to 360°. A square is the most "special" quadrilateral — it satisfies every rule.
Real World
A standard door is a rectangle. A diamond card suit is a rhombus. A ramp cross-section is often a trapezoid. Quadrilaterals are everywhere.
Feeling ready?
Put this concept to work with a practice workout.