An angle bisector is a ray that divides an angle into two congruent angles or two angles that have the same measure.
For example, in the figure below, ray OB shown in red is an angle bisector and it divides angle AOC into two congruent angles.
These two congruent angles are angle AOB and angle COB.
Learn how to find an angle bisector by reading this lesson.
An angle bisector of a triangle is a segment that bisects an angle of that triangle and extends to the opposite side.
In other words, m∠ACE = m∠BCE
In triangle ABC shown above, segment CE is an angle bisector for that triangle.
Segment CE bisects angle ACB and creates angle ACE and angle BCE that are congruent.