This document defines key terms related to parallel lines cut by a transversal including parallel, transversal, angle, vertical angle, corresponding angle, alternate interior angle, and alternate exterior angle. It provides examples of parallel lines cut by a transversal and identifies pairs of angles that are supplementary, vertical, corresponding, and alternate interior. It gives examples of problems identifying angle relationships and setting up and solving equations based on those relationships. Supplementary angles add to 180 degrees, corresponding angles are equal and in the same position relative to the parallel lines, and alternate interior angles are equal and on the inside of the parallel lines on opposite sides of the transversal.