In analogy, when the centred face cuts the Y or Z axis, we have B- or C-centring respectively.
Due to this constraint, the Pearson symbol should only be used to designate simple structures (elements, some binary compound) where the number of atoms per unit cell equals, ideally, the number of translationally equivalent points.
Confusion also arises in the rhombohedral lattice, which is alternatively described in a centred hexagonal (a = b, c, α = β = 90°, γ = 120°) or primitive rhombohedral (a = b = c, α = β = γ) setting.
The more commonly used hexagonal setting has 3 translationally equivalent points per unit cell.
Because there are many possible structures that can correspond to one Pearson symbol, a prototypical compound may be useful to specify.