What type of triangle has exactly one right angle?

A triangle that has exactly one right angle is classified as a right triangle. In geometry, a right triangle is defined by the presence of a 90-degree angle. This right angle distinguishes it from other types of triangles, such as scalene, equilateral, and isosceles triangles.

In a right triangle, the sides opposite the right angle have special relationships defined by the Pythagorean theorem, which states that the sum of the squares of the two legs (the sides forming the right angle) equals the square of the hypotenuse (the side opposite the right angle).

This property is unique to right triangles and does not apply to the other types mentioned. For instance, scalene triangles have all sides of different lengths and do not necessarily include a right angle, equilateral triangles have three equal sides and angles of 60 degrees each, and isosceles triangles have at least two equal sides, but their angles can vary and do not guarantee the presence of a right angle.

Thus, the distinct feature of having exactly one right angle is what categorizes a triangle as a right triangle.