monoclinic (1 diad) simple base-centered 3. orthorhombic (3 perpendicular diads) simple base-centered body-centered face-centered 4. rhombohedral (1 triad) 5. tetragonal (1 tetrad) simple body-centered 6. hexagonal (1 hexad) 7. cubic (4 triads) simple (SC) body-centered (bcc) face-centered (fcc) The simplest and most symmetric, the cubic (or isometric) system, has the symmetry