What is the longest side of a right triangle called?

The longest side of a right triangle is called the hypotenuse. It is always opposite the right angle and is typically denoted by the letter c in the Pythagorean theorem, which states that the square of the hypotenuse is equal to the sum of the squares of the other two sides (a and b): c^2 = a^2 + b^2. The hypotenuse is the longest side in any right triangle, and its length is essential to determine the triangle's shape, angles, and area.