What is the name of the side of the triangle that is directly across from the right angle?

Answer: hypotenuse

Step-by-step explanation:

In a right triangle, the hypotenuse is the longest side, an "opposite" side is the one across from a given angle, and an "adjacent" side is next to a given angle. We use special words to describe the sides of right triangles. The hypotenuse of a right triangle is always the side opposite the right angle.

the side across from a right angle is a hypotenuse