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. It is the longest side in a right triangle.
The other two sides are called the opposite and adjacent sides. These sides are labeled in relation to an angle.
The opposite side is across from a given angle.
The adjacent side is the non-hypotenuse side that is next to a given angle.
Putting it all together from the perspective of angle, A:
And from angle, B:

Practice

Problem 1
Relative to angle G, which side is the adjacent side?
Choose 1 answer:
Choose 1 answer:

Why are these words important?

We're about to learn the trigonometric functions—sine, cosine, and tangent—which are defined using the words hypotenuse, opposite, and adjacent.