# Parallelogram

A parallelogram is a **plane** figure of four sides whose opposite sides are **parallel**. A *rhombus* is a parallelogram with all four sides of equal length; a *rectangle* is a parallelogram whose adjacent sides are **perpendicular**; and a *square* is a parallelogram whose adjacent sides are both perpendicular and equal in length.

The area of a parallelogram is equal to the length of its *base* times the length of its *altitude*.

## Additional topics

Science EncyclopediaScience & Philosophy: *Overdamped* to *Peat*