Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online.n several fields of mathematics the term permutation is used with different but closely related meanings. They all relate to the notion of mapping the elements of a set to other elements of the same set, i.e., exchanging elements of a set. For example, a permutation of may be, or purely. A permutation is simply an ordered arrangement of the elements of a set. In combinatorics, a permutation is usually understood to be a sequence containing each element from a finite set once, and only once.