An angle is bisected when it is cut into two equal parts.
In geometry, bisection is the division of something into two
equal parts, usually by a line, which is then called a bisector.
The most often considered types of bisectors are segment bisectors
and angle bisectors. An angle bisector divides the angle into
two equal angles.
An angle only has one bisector. Each point of an angle bisector
is equidistant from the sides of the angle. The interior bisector
of an angle is the line or line segment that divides it into
two equal angles on the same side as the angle.
For e.g. the angle
ABD is bisected by the line BC. BC is called the bisector.