A right triangle is a special type of triangle that has one angle that measures exactly 90 degrees. This angle is called the right angle.
The other two angles in a right triangle are always less than 90 degrees. The two sides that meet at the right angle are called the legs of the triangle, and the side opposite the right angle is called the hypotenuse.
Right triangles have many special properties and are very important in mathematics, especially in geometry and trigonometry. In fact, the famous theorem about right triangles is called the Pythagorean Theorem. This theorem states that in a right triangle, the square of the length of the hypotenuse is equal to the sum of the squares of the lengths of the legs.
For example, imagine a ladder that is leaning against a wall. The ladder is a right triangle, with the wall as one leg, the floor as another leg, and the ladder as the hypotenuse.