Symmetry with Case 1. Definition. A clique is a complete subgraph, an independent set is an empty subgraph. Definition. R(s, t) is the minimum number s such that any graph on n vertices contains a clique of order s or an independent set of order t. Ex: R(3, 3) = 6. Definition. Rk(s1, . . . , sk) here you color the graph in k colors and want a monochromatic clique of size si in color ci. The “normal” Ramsey number is the special case k = 2.