What is the term for two angles that add up to 90 degrees?

Two angles that add up to 90 degrees are referred to as complementary angles. This term specifically describes the relationship between the angles where their measures sum to form a right angle. Complementary angles can be two separate angles, such as 30 degrees and 60 degrees, or they can be parts of a single figure where they contribute to making a right angle.

In geometry, supplementary angles would refer to two angles that sum up to 180 degrees, which is a distinct and different relationship. Vertical angles are formed when two lines intersect, creating opposite angles that are equal but do not relate directly to the concept of adding to 90 degrees. Adjacent angles are angles that share a common vertex and side but are not defined by their sum—adjacency does not require the angles to sum to any specific value.

Understanding the term "complementary angles" and its correct application helps in identifying relationships between angles in various geometric situations, essential for solving many geometry problems.