Angles on opposite sides of a
transversal and outside the two lines it intersects.
Example
In these figures, angles 2 and 8 are alternate exterior angles.
![](https://media.scolab.com/Illustrations/Lexique/parallel_angles.svg)
When lines are parallel, such as lines d and e, the alternate exterior angles are congruent.
In the figure on the right, angles 2 and 8 have the same measure, as lines d and e are parallel lines. These angles are congruent.