A multimap is a `K -> Set<V>` mapping. - [Multimap on Wikipedia](https://en.wikipedia.org/wiki/Multimap) - [C++'s `std::container::multimap<K, V>`](https://en.cppreference.com/w/cpp/container/multimap.html) [^0] [^0]: As usual with C++ data-structures, order is imposed to keep things "nice" and slower than they should.