A/An __________ triangle contains an angle greater than 90 degrees.

An obtuse triangle is defined as a triangle that has one interior angle measuring greater than 90 degrees. This characteristic distinguishes it from other types of triangles. For example, in an equilateral triangle, all three angles are equal and measure 60 degrees, which means none can exceed 90 degrees. An isosceles triangle can have three different configurations for its angles, but it may still fall within the acute or right categories. A right triangle, by definition, has one angle that is exactly 90 degrees, which means it cannot have an angle greater than that. Therefore, the term "obtuse" specifically captures the essence of what is being asked in the question.