catheti
Cathetus (plural catheti) is a term in Euclidean geometry referring to one of the two sides of a right triangle that form the right angle. The pair of catheti are commonly called the legs of the right triangle. The word derives from the Greek kathetós, meaning perpendicular.
In a right triangle with catheti a and b and hypotenuse c, the Pythagorean theorem holds: a^2
Example: in a 3-4-5 triangle, the catheti have lengths 3 and 4, and the hypotenuse is 5.