Multiset

A multiset is a collection of objects that allows duplicates, meaning the same item can appear multiple times. Unlike a standard set where each element is unique, a multiset keeps track of how many times each element occurs. For example, if you have a multiset with the items {apple, apple, banana}, it shows that "apple" appears twice, and "banana" once. Multisets are useful when the frequency of elements matters, such as inventory counts or word occurrences in a text. They are a flexible way to represent collections where duplicates are meaningful.