# What is Permutation?

In this section we shall determine the number of ways in which we arrange (in order) n distinct elements. We call an arrangement (in order) of n elements a permutation of n distinct elements.

A permutation of n elements is an ordering of the elements such that one element is first; one is second, and so on.
a1, a2, ..., an

For instance, 3, 2, 5, 1, 4 is a permutation of 1, 2, 3, 4, 5. As said earlier, we are interested in the number of different ways in which we can arrange n elements. To demonstrate the argument we begin with the following illustration.