In mathematics, the notion of permutation relates to the act of arranging all the members of a set into some sequence or order, or if the set is already ordered, rearranging (reordering) its elements, a process called permuting.

Alice, Bob and Charlie is different from Charlie, Bob and Alice [2]

permutations, or all possible ways of doing something [2]

Permutations with Repetition [3]

Given a set: P { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 }

How many ways can we choose any 3 elements from the set? (You can select the same element for each selection)

If n is the number of elements in the set, we can always choose n possible ways for each selection.

If r is the number of selections, the total number of permutations would be n x n x n...r number of times or n^{r}