First off, a transversal is a line that overlaps two or more other (typically parallel) lines in geometry. When a transversal cuts two or more lines, the angles that occupy the same relative location are referred to as comparable angles. The matching angles are equivalent when the lines are parallel. When a transversal cuts two lines, the pairs of angles on one side of the transversal and inside the two lines are referred to as the successive interior angles. If a transversal cuts two parallel lines, the pairs of successive interior angles created are supplementary. When a transversal cuts two lines, the pairs of angles on either side of the transversal and inside the two lines are referred to as the alternative interior angles. If a transversal cuts two parallel lines, the alternate interior angles created are congruent. When a transversal cuts two lines, the pairs of angles on either side of the transversal and outside the two lines are referred to as the alternative external angles.
