In mathematics, a permutation of a set is, loosely speaking, an arrangement of its members into a sequence or linear order, or if the set is already ordered, a rearrangement of its elements. The word “permutation” also refers to the act or process of changing the linear order of an ordered set.

Permutations differ from combinations [Combination], which are selections of some members of a set regardless of order. For example, written as tuples, there are six permutations of the set {1, 2, 3}, namely (1, 2, 3), (1, 3, 2), (2, 1, 3), (2, 3, 1), (3, 1, 2), and (3, 2, 1). These are all the possible orderings of this three-element set.

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The number of permutations of n distinct objects is \(n\) factorial, usually written as \(n!\), which means the product of all positive integers less than or equal to \(n\).

Also see: Combination

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## References

*Wikipedia*. https://en.wikipedia.org/w/index.php?title=Permutation&oldid=1125465268.