Given n sites in the plane, the Voronoi diagram divides the plane into regions associated with each site, such that all points in a region are closest to the point associated with that region.

A Voronoi diagram consists of cells associated with a single site, edges, equidistant to two sites, and vertices, equidistant to three sites. Since we assume general position, no four sites can be equidistant to a point in the plane, i.e., no four sites are co-circular.