Complementary angles are two angles whose sum is equal to 90 degrees. In other words, if you add the measures of two complementary angles, you get 90 degrees. Complementary angles are often referred to as "complements" for short. For example, if one angle is 30 degrees, its complement would be 60 degrees.
Supplementary angles, on the other hand, are two angles whose sum is equal to 180 degrees. In other words, if you add the measures of two supplementary angles, you get 180 degrees. Supplementary angles are often referred to as "supplements" for short. For example, if one angle is 120 degrees, its supplement would be 60 degrees.