What term describes two angles whose sum is exactly 90 degrees?

The term that describes two angles whose sum is exactly 90 degrees is "complementary angles." When two angles are complementary, their measures add up to form a right angle. For example, a 30-degree angle and a 60-degree angle are complementary because 30 + 60 = 90 degrees. This concept is fundamental in geometry, particularly when exploring the properties and relationships between different types of angles in shapes and figures.

Adjacent angles refer to angles that share a common vertex and a common side but do not overlap. Supplementary angles are those whose angles sum up to 180 degrees, making them different from complementary angles. Interior angles are angles formed within a shape, such as triangles or polygons, but do not specifically refer to any sum related to 90 degrees. Understanding these distinctions helps clarify why "complementary angles" is the appropriate term for angles that sum to 90 degrees.