is a cycle of length three, since , and , leaving 2 and 5 untouched. We denote such a cycle by , but it could equally well be written or by starting at a different point. The order of a cycle is equal to its length. Cycles of length two are transpositions. Two cycles are "disjoint" if they move disjoint subsets of elements. Disjoint cycles commute: for example, in S6 there is the equality . Every element of S"n" can be written as a product of disjoint cycles; this representation is unique up to the order of the factors, and the freedom present in representing each individual cycle by choosing its starting point.