A set-like object in which order is ignored, but multiplicity is explicitly significant. Therefore, multisets 
and 
are equivalent, but 
and 
differ. The number of multisets of length 
on 
symbols is called 
multichoose 
, denoted 
.
Multiset
See also
Aggregate, Ball Picking, Binomial Coefficient, Choose, Collection, Combination, List, Multichoose, Multinomial Coefficient, Permutation, Set, StringExplore with Wolfram|Alpha
References
Skiena, S. Implementing Discrete Mathematics: Combinatorics and Graph Theory with Mathematica. Reading, MA: Addison-Wesley, p. 12, 1990.Referenced on Wolfram|Alpha
MultisetCite this as:
Weisstein, Eric W. "Multiset." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/Multiset.html