any of six, or sometimes seven, classifications of crystals depending on their symmetry. The classes are cubic, tetragonal, hexagonal, orthorhombic, monoclinic, and triclinic. Sometimes an additional system, trigonal, is distinguished, although this is usually included in the hexagonal system
See also crystal class
crystal system in American English
any of the seven groups (cubic, hexagonal, rhombohedral, tetragonal, orthorhombic, monoclinic, and triclinic) of crystals classified on the basis of the relationships of their crystallographic axes (imaginary lines of reference used to describe the crystal planes)