The (upper) clique number of a graph G, denoted ω(G), is the number of vertices in a maximum clique of G. Equivalently, it is the size of a largest clique or maximal clique of G. The clique number ω(G) of a graph is equal to the largest exponent in the graph's clique polynomial. The lower clique number ω_L(G) may be similarly defined as the size of a graph's smallest maximal clique.