In total there are seven crystal systems&colon; triclinic, monoclinic, orthorhombic, tetragonal, trigonal, hexagonal, and cubic. The CN does not distinguish the geometry of such complexes, i.e. octahedral vs trigonal prismatic. It crystallizes in the trigonal - rhombohedral crystal system. Notable examples include the trigonal prismatic W(CH) and octahedral W(CO). The hexagonal crystal family consists of two crystal systems&colon; trigonal and hexagonal. TiAr is an asymmetrical trigonal bipyramid shape with one bond shorter. It has a trigonal planar molecular geometry. It is a molecule with trigonal planar geometry. The oxide ions are 3-coordinate in a trigonal planar configuration. The trihalides adopt a planar trigonal structure. The trihalides , , , and are all molecular compounds having trigonal pyramidal molecular geometry. Simple bonding theories point to the trigonal planar structure. These bind Cu with high affinity in a trigonal planar geometry. The copper-binding site is described as distorted trigonal pyramidal. The oxygen anions have a coordination number of 3, resulting in a trigonal planar coordination.