The header <unordered_map> defines the class templates
unordered_map and
unordered_multimap; the header <unordered_set> defines the class templates
unordered_set and unordered_multiset.
The exposition-only alias templates
iter-value-type, iter-key-type,
iter-mapped-type, and iter-to-alloc-type
defined in [associative.general] may appear in deduction guides for unordered containers.