What type of triangle has one angle that measures 90 degrees?

A triangle with one angle measuring 90 degrees is classified as a right triangle. The defining characteristic of a right triangle is that it contains one angle that is exactly 90 degrees, which is known as a right angle. This special angle leads to unique properties and theorems specific to right triangles, such as the Pythagorean theorem, which relates the lengths of the sides of the triangle.

In contrast, an acute triangle features all angles measuring less than 90 degrees, meaning no right angle is present. An obtuse triangle contains one angle greater than 90 degrees and therefore cannot be classified as a right triangle as it lacks a right angle. A scalene triangle, while it may or may not have a right angle, is defined by having all sides of different lengths and doesn't directly relate to the measure of its angles. Thus, the presence of a 90-degree angle is what distinguishes a right triangle from all other types of triangles.