hypotenuse – the longest side on a right angle triangle

(pronounced hai-pot-uh-nyoos)

To remember the meaning of hypotenuse, use the following mnemonic:

The high pot was in use (hypotenuse) because it was the longest. 

The hypotenuse is the longest side of a right-angled triangle, and it's always the side opposite the right angle (the 90 degree angle). In any right angle triangle, the other two sides are called the legs, and they form the right angle where they meet. The hypotenuse is special because its length is related to the lengths of the two sides through the famous Pythagorean theorem, which states that the square of the hypotenuse equals the sum of the squares of the other two sides (a² + b² = c² , where c is the hypotenuse). 

This relationship only works for right angled triangles, which is what makes the hypotenuse a fundamental concept in geometry and trigonometry.