ISO 639 is a set of codes that stand for languages. These have various uses including in locale data and tagging web content.
There are several parts, some adopted, some in the process of planning. These are summarized in the table below (which is borrowed from section 6 the Document surveying the localisation situation in Africa.
| ISO 639- | Description | Status | Reference site |
| 1 | 2-letter codes for languages | Existed for several years; formally adopted in 2002 | http://www.loc.gov/standards/iso639-2/php/English_list.php |
| 2 | 3-letter codes for languages & collections | Adopted in 1998 | http://www.loc.gov/standards/iso639-2/php/English_list.php |
| 3 | 3-letter codes for individual languages (comprehensive) | Adopted in 2007 | http://www.sil.org/iso639-3/codes.asp |
| 4 | Guidelines & principles for language encoding | Planned | http://en.wikipedia.org/wiki/ISO_639-4 |
| 5 | 3-letter codes for language groups | Adopted in 2008 | http://www.loc.gov/standards/iso639-5/ |
| 6 | 4-letter codes for language variations | Planned | http://en.wikipedia.org/wiki/ISO_639-6 |
The lists of ISO 639 codes are freely available. They are often reproduced on diverse sites but one should refer to the above sites for authoritative information.
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