**A trapezoid has four sides.** It is a simple, convex quadrilateral with at least one pair of parallel sides. In British English, it is typically called a trapezium.

Formerly, the word trapezoid in British English meant a quadrilateral with no parallel sides, or what is often called an irregular quadrilateral.

Agreement as to the classification of trapezoids is not universal. Some regard only quadrilaterals with one single pair of parallel sides as trapezoids. Others regard the parallelogram, with two pairs of parallel sides, as a special type of trapezoid. This definition includes rectangles, rhombuses and squares as trapezoids as well because they are all special types of parallelogram.