Supplementary angles are two angles whose measures add up to 180 degrees. When two angles are supplementary, they form a straight line and a straight angle. The two angles of a linear pair are always supplementary, but two angles need not be adjacent to be supplementary. For example, 140° and 40° are supplementary angles because they add up to 180° . It is important to note that the two angles that are supplementary to each other do not have to be next to each other. The term "supplementary" comes from the Latin word "supplere," which means "to complete or supply what is needed". To remember the difference between complementary and supplementary angles, one can think of "C" for "Corner" (a right angle) and "S" for "Straight" (180° is a straight line) .