Perpendicular bisector

In a plane, the perpendicular bisector of a line segment is a line such that and are perpendicular and passes through the midpoint of .

In 3-D space, for each plane passing through there is a distinct perpendicular bisector. The set of lines which are perpendicular bisectors of form a plane which is the plane perpendicularly bisecting .

In a triangle, the perpendicular bisectors of all three sides intersect at the circumcenter.