چندمجموعه

Also known as bag, mset

In mathematics, a multiset (or bag, or mset) is a modification of the concept of a set that, unlike a set, allows for multiple instances for each of its elements. The number of instances given for each element is called the multiplicity of that element in the multiset. As a consequence, an infinite number of multisets exist that contain only elements and , but vary in the multiplicities of their elements: The set contains only elements and , each having multiplicity 1 when is seen as a multiset. In the multiset , the element has multiplicity 2, and has multiplicity 1. In the multiset , and