 As a consequence, BCP 47 language tags that include a primary language subtag for a collection may be ambiguous as to whether the collection is intended to be inclusive or exclusive.ISO 639-5 does not define precisely which languages are members of these collections; only the hierarchical classification of collections is defined, using the inclusive definition of these collections.Because of this, RFC 5646 does not recommend the use of subtags for language collections for most applications, although they are still preferred over subtags whose meaning is even less specific, such as "Multiple languages" and "Undetermined".