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.

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**.