A subperiodic group is a group of Euclidean mappings such that its translations form a
A crystallographic subperiodic group in n-dimensional space is a subperiodic group for which the group of linear parts is a crystallographic point group of n-dimensional space. The crystallographic subperiodic groups in two and three-dimensional space are classified in:
friezegroups: 7 two-dimensional groups with one-dimensional translations;
- rod groups: 75 three-dimensional groups with one-dimensional translations;
- layer groups: 80 three-dimensional groups with two-dimensional translations.
International Tables of Crystallography, Volume E