“…Let S be a semigroup and T be a nonempty subset of S. The Cayley graph Cay(S, T ) of S relative to T is defined as the graph with vertex set S and edge set E(Cay(S, T )) consisting of those ordered pair (a, b), where a = b and sa = b for some s ∈ T (see, [5,7,14]). The Cayley graphs of semigroups have been investigated by many authors, and a lot of interesting results have been obtained (see, [8][9][10][11][12][13][16][17][18]). The Cayley graphs of semigroups are closely related to finite state automata and have many valuable applications (see, [5-9, 11-13, 18-20]).…”