Perpendicular bisector

A perpendicular bisector is a line that crosses a segment at its midpoint and at a right angle. Every point on it is equally distant from the segment’s endpoints.

Locus: A locus is the set of points satisfying a specified condition. The points equidistant from a segment’s endpoints form this line.
Compass-and-straightedge construction: A compass-and-straightedge construction creates geometric figures using an unmarked ruler and a compass. These tools construct a segment’s perpendicular bisector without measuring angles or lengths.
Line segment: A line segment is the part of a line bounded by two endpoints. The perpendicular bisector is defined relative to this finite geometric object.
Angle bisector: An angle bisector is a ray or line that divides an angle into two equal angles. It bisects an angle rather than a segment.
Equidistant: Equidistant points are at equal distances from two or more specified objects. Every point on the perpendicular bisector is equidistant from the segment’s endpoints.
Circumscribed circle: A circumscribed circle passes through every vertex of a polygon. Intersecting side bisectors locates the center of a triangle’s circumscribed circle.
Angle: An angle is the figure formed by two rays sharing an endpoint. A right angle specifies how the bisector meets the segment.
Median (geometry): A median of a triangle is a segment joining a vertex to the midpoint of the opposite side. It passes through a midpoint but need not meet the side at a right angle.
Midpoint: The midpoint of a segment is the point halfway between its endpoints. The line crosses the segment at this defining point.
Voronoi diagram: A Voronoi diagram partitions a space into regions nearest to each of a set of sites. Boundaries between two sites lie along their connecting segment’s perpendicular bisector.

Linked from 18 pages