Definition
In a right triangle, the hypotenuse is the side opposite the right angle (the 90° corner). It is always the longest of the three sides.
Plain English
The slanted side of a triangle that has one square corner. It connects the ends of the two straight sides that meet at that square corner, and it is always the longest side.
Context Anchor
Seen in aviation maintenance math, drawings, layout work, and measurement problems that use right triangles.
Derivation
From the Greek hypoteinousa, meaning 'stretching under.' In a right triangle drawn with the square corner at the top, the hypotenuse is the side that stretches underneath, connecting the two other sides.
Why Pilots Care
Maintenance technicians use the hypotenuse when applying the Pythagorean theorem (a² + b² = c²) to figure out distances, diagonal cuts, and angled measurements on aircraft structures and sheet metal.
Analogy
If a ladder leans against a wall, the wall and ground make the square corner, and the ladder acts like the hypotenuse.
Intuition Check
Do not identify the hypotenuse by which side looks longest first. First find the 90-degree angle; the side directly across from it is the hypotenuse.
Example Sentence 1
After measuring the two short sides of the bracket at 3 inches and 4 inches, the technician calculated the hypotenuse as 5 inches.
Example Sentence 2
Knowing the two legs of the triangle allowed the technician to calculate the exact length of the hypotenuse needed for the replacement part.