The language code table is based on ISO 639 standard which is issued in several parts:
- ISO 639-1 contains strictly two alphabetic letters, called α-2,
- ISO 639-2/B "B" = bibliographic – α-3 is used for bibliographic purpose,
- ISO 639-2/T "T" = terminology – α-3 is used for technical purpose,
- ISO 639-3 α-3 covers all the languages and macro-languages of the world; the values are compliant with ISO 639-2/T.