Permutation

Permutation

A rearrangement of the elements in an ordered list S into a one-to-one correspondence with S itself. Combinatorics studies the number of possible ways of doing this under various conditions.

There are basically two types of permutation:

1. Repetition is Allowed also known as permutations with repetition
2. No Repetition: for example the first three people in a running race. You can't be first and second, also known as permutations without repetition.