Ordering (original) (raw)
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The number of "arrangements" in an ordering of 
items is given by either a combination (order is ignored) or a permutation (order is significant).
An ordering (or order) is also a method for choosing the order in which elements are placed (i.e., a sorting function).
The Wolfram Language function Ordering[_p_] gives the inverse permutation of a given permutation 
.
See also
Arrangement, Combination, Cutting, Derangement,Inverse Permutation, Lexicographic Order, Monomial Order, Ordering Axioms, Partial Order, Permutation,Sorting, Total Order,Transposition Order, Well Ordered Set
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Cite this as:
Weisstein, Eric W. "Ordering." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/Ordering.html