Definitions for

**"Derangement"**a permutation of the elements of a set such that no element stays in the same place

In combinatorial mathematics, a derangement is a permutation that leaves no element unpermuted. That is, it is a bijection Ï† from a set S into itself with no fixed points: for all x in S, Ï†(x) ≠ x. A frequent problem is to count the number of derangements as a function of the number of elements of the set, often with additional constraints; these numbers are called subfactorials and are a special case of the rencontres numbers.

The act of deranging or putting out of order, or the state of being deranged; disarrangement; disorder; confusion; especially, mental disorder; insanity.

a state of mental disturbance and disorientation

the act of disturbing the mind or body; "his carelessness could have caused an ecological upset"; "she was unprepared for this sudden overthrow of their normal way of living"