Trapezium

There are two common definitions of the trapezium. The American definition is a Quadrilateral with no Parallel sides. The British definition for a trapezium is a Quadrilateral with two sides Parallel. Such a trapezium is equivalent to a Trapezoid and therefore has Area

$$A={\textstyle{1\over 2}}(a+b)h.$$

See also Diamond, Lozenge, Parallelogram, Quadrilateral, Rhomboid, Rhombus, Skew Quadrilateral, Trapezoid