Complementary angles are a pair of angles whose measures add up to 90 degrees. When two angles are complementary, each angle is said to be the complement of the other. For example, if one angle measures 30 degrees, its complement would be an angle measuring 60 degrees, because 30 + 60 equals 90.

An angle is a measure of rotation or turning and is usually measured in degrees or radians. In geometry, an angle is the figure formed by two rays, called the sides of the angle, sharing a common endpoint, called the vertex. The size of an angle is determined by the amount of rotation from one ray to the other.

Degrees are a unit of measurement for angles, representing the rotation between two rays. The degree angle system divides a full rotation into 360 units called degrees.

Supplementary angles are a pair of angles that add up to 180 degrees. When two angles are supplementary, each angle is said to be the supplement of the other.