In computer science, a multimap (sometimes also multihash, multidict or multidictionary) is a generalization of a map or associative array abstract data type in which more than one value may be associated with and returned for a given key.
[4] Apache Commons Collections provides a MultiMap interface for Java.
[5] It also provides a MultiValueMap implementing class that makes a MultiMap out of a Map object and a type of Collection.
[7] Kotlin does not have explicit support for multimaps,[8] but can implement them using Maps with containers[9] for the value type.
OCaml's standard library module Hashtbl implements a hash table where it's possible to store multiple values for a key.