Editing Crystal system (section)

{{Short description|Classification of crystalline materials by their three-dimensional structural geometry}}
{{More citations needed|date=September 2020}}
[[File:Carbon lattice diamond.png|thumb|The [[Diamond cubic|diamond crystal structure]] belongs to the face-centered [[cubic crystal system|cubic lattice]], with a repeated two-atom pattern.]]

In [[crystallography]], a '''crystal system''' is a set of [[Crystallographic point group|point groups]] (a group of geometric symmetries with at least one fixed point). A '''lattice system''' is a set of [[Bravais lattices]] (an infinite array of discrete points). [[Space group]]s (symmetry groups of a configuration in space) are classified into crystal systems according to their point groups, and into lattice systems according to their Bravais lattices. Crystal systems that have space groups assigned to a common lattice system are combined into a '''crystal family'''.

The seven crystal systems are [[Triclinic crystal system|''triclinic'']], [[Monoclinic crystal system|''monoclinic'']], [[Orthorhombic crystal system|''orthorhombic'']], [[Tetragonal crystal system|''tetragonal'']], [[Hexagonal crystal family|''trigonal'', ''hexagonal'']], and [[Cubic crystal system|''cubic'']]. Informally, two crystals are in the same crystal system if they have similar symmetries (though there are many exceptions).