Also found in: Dictionary, Thesaurus, Wikipedia.
parallelogram,closed plane figure bounded by four line segments, or sides, with opposite pairs of sides parallel and equal in length. The rhombus, rectangle, and square are special types of parallelograms. Any side of a parallelogram is a base; an altitude is the perpendicular distance from a base to the opposite parallel side. The area of a parallelogram is equal to the product of the lengths of its base and altitude. The diagonals of a parallelogram, connecting opposite vertices, bisect one another; either diagonal divides the parallelogram into two congruent triangles.
a quadrangle whose opposite sides are parallel (see Figure 1). A parallelogram can also be defined as a convex quadrangle that satisfies any of the following conditions: (1) both pairs of opposite sides consist of equal line segments; (2) one pair of opposite sides consists of equal and parallel segments;
(3) each pair of opposite vertices has equal angles; or (4) the diagonals’ point of intersection bisects each diagonal. Figure 1 illustrates different types of parallelograms, including the rectangle (Figure 1,b), a parallelogram whose angles are right angles; the rhombus (Figure l,c), an equilateral parallelogram; and a square (Figure 1,d), an equilateral rectangle.