A symbolic notation devised by W. B. Pearson for indicating the structure of a crystal. There are three parts:

1. (1) A lower case letter denoting one of six crystal systems: a=anorthic (triclinic); m=monoclinic; o=orthorhombic; t=tetragonal; h=hexagonal or rhombohedral; c=cubic.

2. (2) An upper-case letter denoting the lattice type: P=primitive; I=body-centred; F=face-centred (full); C=face-centred (side); R=rhombohedral.

3. (3) A number giving the number of atoms in the unit cell.

For example, sodium chloride has a cubic, face-centred structure with eight atoms in the unit cell, so has Pearson symbol cF8. The first two letters of a Pearson symbol give the Bravais lattice.