Let * G = (N,E) * be a graph , and let
* x * and * y * be distinct nodes of * G * that
aren't joined by an edge. The graph * G/xy * formed by adding
the edge * (x,y) * to * G * is called a join of * G *.

A - B - C - D - E - F - G - H - I - J - K - L - M - N - O - P - Q - R - S - T - U - V - W - X - Y - Z

An On-line Dictionary of Combinatorics