A quadrilateral is a polygon with four sides and four angles.

The main types of quadrilaterals are squares, rectangles, rhombuses, trapezoids, and parallelograms.

A square is a quadrilateral with four equal sides and four right angles.

A rectangle is a quadrilateral with opposite sides equal and four right angles.

A rhombus is a quadrilateral with all four sides equal in length, but angles are not necessarily right angles.

A trapezoid is a quadrilateral with at least one pair of parallel sides.

A triangle has three sides.