Let R is a relation on a set A, that is, R is a relation from a set A to itself. Then R R, the composition of R with itself, is always represented. Also, R R is sometimes denoted by R 2. Similarly, R 3 = R 2 R = R R R, and so on. Thus R n is defined for all positive n. Example1: Let X = {4, 5, 6}, Y = {a, b, c} and Z = {l, m, n}.