A parallelogram is a quadrilateral with two sets of parallel sides. The opposite sides of a parallelogram are of equal length, and the opposite angles of a parallelogram are congruent. The three-dimensional counterpart of a parallelogram is a parallelepiped.
- Two parallel sides are of equal length.
- Area, A, of a parallelogram is A = BH, where B is the base of the parallelogram and H is its height.
- Area of a parallelogram is twice the area of a triangle created by one of its diagonals.
- Diagonals of a parallelogram bisect each other.
- Parallelogram is a special case of the trapezoid.
- Rectangle is a special case of the parallelogram.
- Rhombus is a special case of the parallelogram.