Primitive cell of the real-space Bravais lattice — all points closer to the origin than to any other lattice point
The Wigner-Seitz cell is constructed by drawing perpendicular bisectors to all nearest-neighbor vectors and taking the smallest enclosed region. It is identical to the Voronoi cell of the lattice. In reciprocal space, the same construction gives the first Brillouin zone — the fundamental domain for Bloch's theorem. The WS cell has the full point-group symmetry of the lattice.