of points and the origin are coplanar if and only if the matrix of the coordinates of the points is of rank 2 or less. Geometric shapes A skew polygon is a polygon whose vertices are not coplanar. Such a polygon must have at least four vertices; there are no skew triangles. A polyhedron that has positive volume has vertices that are not all coplanar. See also Collinearity Plane of incidence References External links Planes (geometry)