Hypotenuse

Part of speech: noun

Pronunciation: /haɪˈpɒtənjuːz/

Definitions

1. The longest side of a right triangle, opposite the right angle
2. In a right-angled triangle, this is the side that is directly opposite the right angle and is known to be the longest side
3. This term refers to the side of a right triangle that is longest, lying opposite the right angle

Etymology: The Greek mathematicians who first named this side were describing a geometric action rather than a shape. In ancient Greek, "hupoteínousa pleurá" meant "side stretching under," because the side is imagined as stretched beneath the right angle, spanning the gap between the other two sides. The phrase came from "hupoteínō," meaning "to subtend" or "stretch under," and the feminine adjective was used with "pleurá," the word for side. The Greeks shortened the phrase to just the adjective, and it passed into Latin as "hypotenusa." Its English use is a direct borrowing from that Latin form, so the word carries a precise geometric idea inside it: the side that is stretched under the right angle, opposite to it. That image explains why the term refers to a position in the triangle rather than to length, even though this side turns out to be the longest.

Synonyms: longest side