) The hexagonal lattice system is larger than the hexagonal crystal system, and consists of the hexagonal crystal system together with the 18 groups of the trigonal crystal system other than the seven whose names begin with R.The Bravais lattice of the space group is determined by the lattice system together with the initial letter of its name, which for the non-rhombohedral groups is P, I, F, or C, standing for the principal, body centered, face centered, or C-face centered lattices.
Če je sistem trigonalen, je kristalna mreža heksagonalna, dokler je prostorska skupina ena od sedmih skupin v romboedričnem mrežnem sistemu, ki je sestavljen iz sedmih trigonalnih prostorskih skupin v zgornji preglednici, katerih imena se začenjajo s črko R. (Izraz romboedrski se včasih uporablja tudi kot alternativno ime za celoten trigonalni sistem).