- published: 04 Apr 2015
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ISO 639 is a set of standards by the International Organization for Standardization that is concerned with representation of names for language and language groups.
It was also the name of the original standard, approved in 1967 (as ISO 639/R) and withdrawn in 2002. The ISO 639 set consists of six different parts.
The language codes defined in the several sections of ISO 639 are used for bibliographic purposes and, in computing and internet environments, as a key element of locale data. The codes also find use in various applications, such as Wikipedia URLs for its different language editions.
A multilingual page is contained by the CSS class "multilingual", with text in every language contained within the class "lang-xx", where xx is a lowercase ISO 639 two-letter or three-letter language code and the lang attribute. The lang attribute is contextually more correct, but the CSS required to hook into it is not supported by all browsers. If there is no two-letter code, the lowercase three-letter code is used. For text in an unknown language "und", (undetermined) is used.