A trapezoid is a quadrangle that is not a parallelogram. A trapezoid is a quadrangle because it has four sides and four internal angles, but it is not a parallelogram because it only has one pair of parallel sides rather than two.
Each of the two parallel sides is called a base of the trapezoid, and each of the two non-parallel sides is referred to as a leg. The perimeter of the trapezoid is determined by adding the lengths of all four sides together. The formula for the area of the trapezoid requires multiplying the height by the sum of both bases and dividing by two.