A leg of a triangle is one of its sides. For a right triangle, the term "leg" generally refers to a side other than the one opposite the right angle (which is termed the hypotenuse). Legs are also known as catheti.
Leg
See also
Cathetus, Hypotenuse, TriangleExplore with Wolfram|Alpha
Cite this as:
Weisstein, Eric W. "Leg." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/Leg.html