A Classification Index can exist in several languages. Indicates the languages available. If a Classification Index exists in several languages, the number of entries in each language may be different, as the number of terms describing the same phenomenon can change from one language to another. However, the same phenomena should be described in each language. Language is expressed using standard RFC 1766 language codes (for example: fr, en) and may be extended with the use of specific locations (en-UK).