Which angles are also referred to as vertical angles?

Vertical angles are defined as the pairs of angles that are formed when two lines intersect. Specifically, when two lines cross each other, they create four angles, and the pairs of angles that are opposite each other are considered vertical angles. These angles share the same vertex and are formed by the intersecting lines.

This definition aligns perfectly with the description provided in the correct answer choice, emphasizing both the formation of angles and their relationship to a common vertex. The essential characteristic of vertical angles is that they are always equal in measure, which is a vital concept in geometry that can be used to solve various problems involving angle relationships.