Unit cell

The Wigner–Seitz cell of the reciprocal lattice in momentum space is called the Brillouin zone.

For each particular lattice, a conventional cell has been chosen on a case-by-case basis by crystallographers based on convenience of calculation.

[7] For any 2-dimensional lattice, the unit cells are parallelograms, which in special cases may have orthogonal angles, equal lengths, or both.

For any 3-dimensional lattice, the conventional unit cells are parallelepipeds, which in special cases may have orthogonal angles, or equal lengths, or both.

Seven of the fourteen three-dimensional Bravais lattices are represented using conventional primitive cells, as shown below.