ISO 639-3:2007, Codes for the representation of names of languages — Part 3: Alpha-3 code for comprehensive coverage of languages, is an international standard for language codes in the ISO 639 series. The standard describes three‐letter codes for identifying languages. It extends the ISO 639-2 alpha-3 codes with an aim to cover all known natural languages. The standard was published by ISO on 2007-02-05.
It is intended for use in a wide range of applications, in particular computer systems where many languages need to be supported. It provides an enumeration of languages as complete as possible, including living and extinct, ancient and constructed, major and minor, written and unwritten. However, it does not include reconstructed languages such as Proto-Indo-European.
It is a superset of ISO 639-1 and of the individual languages in ISO 639-2. ISO 639-1 and ISO 639-2 focused on major languages, most frequently represented in the total body of the world's literature. Since ISO 639-2 also includes language collections and Part 3 does not, ISO 639-3 is not a superset of ISO 639-2. Where B and T codes exist in ISO 639-2, ISO 639-3 uses the T-codes.