FACET

Facet - A face of a convex set, not equal to the set, of maximal dimension. If the set is polyhedral, say P = (x: Ax <= b), where the defining inequalities are irredundant , the facets are in 1-1 correspondence with (x in P: A(i, .)x = b_i) for i such that the equality is not forced – i.e., there exists x in P for which A(i, .)x < b_i.