What are the opposite congruent angles formed by intersecting lines known as?

When two lines intersect, they create pairs of angles that are opposite each other at the point of intersection. These angles are referred to as vertical angles. Vertical angles are always congruent, meaning they have the same measure. For example, if one angle measures 50 degrees, the angle directly opposite it will also measure 50 degrees.

This property arises because when two lines intersect, they form two pairs of vertical angles. The intersection causes the angles to 'mirror' each other across the point where the lines meet. In contrast, complementary angles are two angles that add up to 90 degrees, adjacent angles are angles that share a common side and a common vertex but do not overlap, and supplementary angles are two angles that add up to 180 degrees. Understanding these definitions helps clarify why the segments formed by intersecting lines are specifically called vertical angles.