A symbol of the form {p,q,r,...} used to describe regular polygons, polyhedra, and their higher-dimensional counterparts.
The symbol {p} denotes a regular polygon. The symbol {p,q} denotes a tessellation of regular p-gons, with q of them surrounding each vertex. The Schläfli symbol can also be used to describe Platonic solids and Kepler-Poinsot solids, and a generalized version describes quasiregular polyhedra and Archimedean solids. Higher dimensional symbols can be used to describe the regular polychora and polytopes.
The symbol has the particularly nice property that its reversal gives the symbol of the dual polyhedron.