A trapezium is a quadrilateral that consists of four sides that are not parallel. If one pair of these sides were parallel, it would be called a trapezoid. If both pairs were parallel, it would be a parallelogram.
The area of a trapezium is calculated by dividing it into two triangles. The sum of the areas of those two triangles is the area of the trapezium. The perimeter of a trapezium is calculated by adding the lengths of its four sides. In Britain, the meaning of trapezium and trapezoid are reversed compared to the American definition. The etymology of trapezium dates back to the Late Latin word with the same spelling that meant "little table."