A trapezoid is a quadrilateral with two parallel sides and, usually, two nonparallel sides. A quadrilateral is a geometric shape that has four sides. Some specialized types of trapezoid are the parallelogram and the isosceles trapezoid.
The two parallel sides of a trapezoid are its bases while the legs are the nonparallel sides. Geometric analysis of a trapezoid includes calculating the height, median and area. The height of a trapezoid is a line segment that runs perpendicular to the bases. The median, or mid-segment, is a line that is parallel to the bases and connects the midpoints of each leg. The area is calculated with a formula using the lengths of each base and the height.
A parallelogram is usually defined as a trapezoid, although it has two pairs of parallel sides instead of just one. An isosceles trapezoid has congruent base angles and equal leg lengths.