Definition:Quadrilateral/Parallelogram/Altitude

Definition

 * Parallelogram.png

An altitude of a parallelogram is a line drawn perpendicular to its base, through one of its vertices to the side opposite to the base (which is extended if necessary).

In the parallelogram above, line $DE$ is an altitude of the parallelogram $ABCD$.

The term is also used for the length of such a line.