A multiset, also known as a bag is a collection of things, but—unlike a set, which is also a collection of things—the same object can occur in a multiset more than once. For instance, the sets {1, 2}, {1, 2, 2}, and {1, 1, 1, 1, 1, 2, 2} are all equal, while the multisets [1, 2], [1, 2, 2], and [1, 1, 1, 1, 1, 2, 2] are all different. However, order does not matter for sets or for multisets, so, for instance {1, 2} = {2, 1} and [1, 1, 1, 1, 1, 2, 2] = [2, 1, 1, 2, 1, 1, 1].