ISO/TC 37/SC 2/WG 1 - Language varieties

ISO 639-4:2010 gives the general principles of language coding using the codes that are specified in the other parts of ISO 639 and their combination with other codes. It also lays down guidelines for the use of any combination of the parts of ISO 639. The terminology and general descriptions of ISO 639-4 are intended to replace corresponding text of other parts of ISO 639 as relevant in future revisions. Relevant metadata for the description of linguistic entities are given, as a framework for databases of linguistic data to support the ISO 639 series.

ISO 639-5:2008 provides a code consisting of language code elements comprising three-letter language identifiers for the representation of names of living and extinct language families and groups. Languages designed exclusively for machine use, such as computer-programming languages, are not included in this code.

ISO 639-3:2007 provides a code, published by the Registration Authority of ISO 639-3, consisting of language code elements comprising three-letter language identifiers for the representation of languages. The language identifiers according to this ISO 639-3:2007 were devised for use in a wide range of applications, especially in computer systems, where there is potential need to support a large number of the languages that are known to have ever existed. Whereas ISO 639-1 and ISO 639-2 are intended to focus on the major languages of the world that are most frequently represented in the total body of the world's literature, ISO 639-3:2007 attempts to provide as complete an enumeration of languages as possible, including living, extinct, ancient and constructed languages, whether major or minor, written or unwritten. As a result, ISO 639-3:2007 deals with a very large number of lesser-known languages. Languages designed exclusively for machine use, such as computer-programming languages and reconstructed languages, are not included in this code.

This part of ISO 639 provides a code consisting of language code elements comprising two-letter language identifiers for the representation of names of languages. The language identifiers according to this part of ISO 639 were devised originally for use in terminology, lexicography and linguistics, but may be adopted for any application requiring the expression of language in two-letter coded form, especially in computerized systems. The alpha-2 code was devised for practical use for most of the major languages of the world that are not only most frequently represented in the total body of the world's literature, but which also comprise a considerable volume of specialized languages and terminologies. Additional language identifiers are created when it becomes apparent that a significant body of documentation written in specialized languages and terminologies exists. Languages designed exclusively for machine use, such as computer-programming languages, are not included in this code.

ISO 639-6:2009 specifies a method for establishing four-letter language identifiers (alpha-4) and language reference names for language variants and a hierarchical framework for relating them to languages, language families and language groups. The alpha-4 language identifiers have been developed for use in a wide range of applications, especially in computer systems, where there is a potential need to cover the entire range of languages, language families and language groups as well as language variants within each identified language. Alpha-4 language identifiers can support the quantity of known language variants and accommodate any future expansion. ISO 639-6:2009 provides a hierarchical framework, which facilitates backward compatibility with other ISO 639 codes, based on linguistic and/or geolinguistic relationships, within which a comprehensive enumeration of language variants is possible, including living, extinct, ancient and constructed languages, whether major or minor. As a result, ISO 639-6:2009 caters for a very large number of languages and their variants. ISO 639-6:2009 is not applicable to the registrations for languages designed exclusively for machine use, such as computer-programming languages and reconstructed languages.