Mathematicians use some technical terms when discussing tilings. An "edge" is the intersection between two bordering tiles; it is often a straight line. A "vertex" is the point of intersection of three or more bordering tiles. Using these terms, an "isogonal" or vertex-transitive tiling is a tiling where every vertex point is identical; that is, the arrangement of polygons about each vertex is the same. The fundamental region is a shape such as a rectangle that is repeated to form the tessellation. For example, a regular tessellation of the plane with squares has a meeting of four squares at every vertex.