Points in three-dimensional
space are coplanar when they are in the same plane.
B,C,D and E are coplanar but A,B,C and D are not. Any three points
are coplanar. For example, A,B, and C are coplanar, A,E,C are coplanar
etc and three distinct points are always coplanar; but four points
in space are usually not coplanar.