Bag

In mathematics, a "bag" is an unordered list. A bag differs from a set in that it can contain the same value more than once. A bag differs from a list in that its elements are not ordered. For example, $\mathrm{Bag}(1,1,2,3)=\mathrm{Bag}(2,1,3,1)\ne \mathrm{Bag}(1,2,3).$