## Definition

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.

## Also known as

The length of the altitude of a parallelogram is also known as its height, but as this term is less precise it is not recommended.