Face - The plane surface or faces are the most obvious feature of crystals are parallel to net-planes in the crystal structure.
Forms - A crystal is made up entirely of like faces is termed a simple form. A crystal which consist of two or more simple forms is called combination.
Edge - An edge is formed by the intersection of two faces.
Solid Angles - A solid angle is formed by the intersection of three or more faces.
Interfacial angle - The angle between any two faces of a crystal is termed the interfacial angle.