Question

When do you say that a line is the perpendicular bisector of another line?

Answer 1

Perpendicular bisector.

When two lines intersect at $90$ degrees or at right angles, they are said to be perpendicular to each other. A bisector, on the other hand, is a line that splits a line into two equal halves. A perpendicular bisector of a line segment AB intersects AB at 90 degrees and divides it into two equal halves.