1. Angles : Complementary Angles R A B C P Q Two angles that add up to 90° are called complementary angles.

2. Angles : Supplementary Angles R A B C P Q Two angles that add up to 180° are called supplementary angles.

3. Angles : Adjacent Angles R A P Q Two angles that share a common side and a common vertex, but do not overlap are called adjacent angles.  AQP and  PQR are adjacent angles.

4. Angles : Linear Pair of Angles R A P Q When two adjacent angles are supplementary angles of each other, they form a linear pair of angles.  AQP and  PQR is a linear pair of angles.