Triangles are fundamental shapes in geometry, but one special type stands out for its unique properties: the right-angled triangle, or simply, the right triangle. Its defining feature is one angle that measures exactly 90 degrees, forming a perfect corner like you'd find on a square or a sheet of paper.

Because of this special angle, the sides of a right triangle also get special names. The two sides that meet to form the 90-degree angle are called the legs.

The third side, which is always opposite the right angle, is called the hypotenuse. It's also always the longest side of the triangle. Being able to spot the right angle helps you immediately identify which side is the hypotenuse and which two are the legs.

Right triangles have another interesting property related to their angles. The three angles in any triangle always add up to 180 degrees. Since a right triangle uses up 90 of those degrees for its right angle, the other two angles must share the remaining 90 degrees.

Understanding these basic parts is the first step toward exploring some of the most powerful ideas in geometry. Let's see if you've got it down.