Which type of triangle has exactly one angle greater than 90 degrees?

An obtuse triangle is defined as a triangle that possesses one angle measuring greater than 90 degrees, which distinguishes it from other types of triangles. In an obtuse triangle, the angle exceeding 90 degrees is known as the obtuse angle, while the other two angles must always be acute, each measuring less than 90 degrees. This characteristic ensures that the sum of the angles in any triangle, which is always 180 degrees, remains satisfied.

In contrast, an acute triangle is made up of three angles, each less than 90 degrees. A right triangle includes one angle that is exactly 90 degrees, while an equilateral triangle has three angles that are all equal and each measuring 60 degrees. Thus, the presence of an angle greater than 90 degrees is what specifically defines the obtuse triangle, making it the correct answer in this scenario.