A locus (plural loci) is the set of all points that follow a given rule.
The locus of points a fixed distance from a point is a circle. The locus of points a fixed distance from a straight line is a pair of parallel lines. Points equidistant from two points lie on the perpendicular bisector.
Remember
- Fixed distance from a point → circle.
- Equidistant from two points → perpendicular bisector.