What term describes angles that add up to 180 degrees?

Angles that add up to 180 degrees are defined as supplementary angles. This concept is fundamental in geometry, as it illustrates how two angles can combine to form a straight line. When two angles are supplementary, their measures sum to exactly 180 degrees, which is crucial in various geometric applications, such as determining unknown angle measures, solving problems involving parallel lines and transversals, and analyzing polygon properties.

For instance, if one angle measures 120 degrees, the supplementary angle would measure 60 degrees, making their total 180 degrees. Understanding supplementary angles is essential for students as it helps build a foundation for more complex geometric concepts. This term is distinct from others: complementary angles, for example, are those that add up to 90 degrees, which is a different relationship. Similarly, adjacent angles share a common side and vertex but are not necessarily related by their angle measures. Linear angles typically refer to adjacent angles that, when combined, create a straight line, essentially falling under the category of supplementary angles but are not used as the standard term to define their relationship.

Therefore, recognizing that supplementary angles sum to 180 degrees is key to mastering basic geometric principles.