# Definition:Perpendicular Bisector

## Definition

Let $AB$ be a line segment.

The perpendicular bisector of $AB$ is the straight line which:

is perpendicular to $AB$
passes through the point which bisects $AB$.

## Also known as

The perpendicular bisector of a line segment is also known as its mediator.

## Also see

It follows from the parallel postulate that, in Euclidean geometry, the perpendicular bisector for any given line segment is unique.