Trapezoid

Trapezoid (AmE) Trapezium (BrE)
Trapezoid or trapezium
Type	quadrilateral
Edges and vertices	4
Area	${\displaystyle {\tfrac {a+b}{2}}h}$
Properties	convex

Look up trapezoid in Wiktionary, the free dictionary.

In geometry, a trapezoid (/ˈtræpəzɔɪd/) in North American English, or trapezium (/trəˈpiːziəm/) in British English,^[1][2] is a quadrilateral that has one pair of parallel sides.

The parallel sides are called the bases of the trapezoid. The other two sides are called the legs (or the lateral sides) if they are not parallel; otherwise, the trapezoid is a parallelogram, and there are two pairs of bases. A scalene trapezoid is a trapezoid with no sides of equal measure,^[3] in contrast with the special cases below.

A trapezoid is usually considered to be a convex quadrilateral in Euclidean geometry, but there are also crossed cases. If ABCD is a convex trapezoid, then ABDC is a crossed trapezoid. The metric formulas in this article apply in convex trapezoids.