Trapezoid
In Euclidean geometry, a convex quadrilateral with at least one pair of parallel sides is referred to as a
trapezoid in American and Canadian English but as a
trapezium in English outside North America. The parallel sides are called the
bases of the trapezoid and the other two sides are called the
legs or the lateral sides. A
scalene trapezoid is a trapezoid with no sides of equal measure, in contrast to the special cases below. There is some disagreement whether parallelograms, which have two pairs of parallel sides, should be regarded as trapezoids. Some define a trapezoid as a quadrilateral having
only one pair of parallel sides, thereby excluding parallelograms. Others define a trapezoid as a quadrilateral with
at least one pair of parallel sides, making the parallelogram a special type of trapezoid. The latter definition is consistent with its uses in higher mathematics such as calculus. The former definition would make such concepts as the trapezoidal approximation to a definite integral ill-defined. This article uses the inclusive definition and considers parallelograms as special cases of a trapezoid.