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ISO 639-3 is an international standard for language codes. It extends the ISO 639-2 alpha-3 codes with an aim to cover all known natural languages. The draft version has been already used by the 15th edition Ethnologue. The standard was published by ISO on 5 February 2007.
It's 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.
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, whereas 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, it uses the T-codes.
|Arabic||ar||ara||macro||arb + several others|
The final standard contains 7589 entries. The inventory of languages is based on three sources: the individual languages contained in 639-2 are the basis, this was extended by modern languages from the Ethnologue 15th edition, and by historic varieties, ancient languages and artificial languages from Anthony Aristar at the Linguist List.
A transition from ISO 639-1 could be done with List of ISO 639-1 codes.
 Code space
Since the code is three-letter alphabetic, one upper bound for the number of languages that can be represented is 26 × 26 × 26 = 17576. Since ISO 639-2 defines special codes (2), a reserved range (520) and B-only codes (23), 545 codes cannot be used in part 3. Therefore a lower upper bound is 17576 - 545 = 17032.
The upper bound gets even lower if one subtracts the language collections defined in 639-2.
There are 56 languages in ISO 639-2 which the SIL considers to be "macrolanguages" in 639-3 .
Some of these macrolanguages had no individual language as defined by 639-3 in ISO 639-2, e.g. 'ara'. Others like 'nor' had their two individual parts ('nno', 'nob') already in 639-2.
That means some languages (e.g. 'arb') that were considered by ISO 639-2 to be dialects of one language ('ara') are now in ISO 639-3 in certain contexts considered to be individual languages themselves.
This is an attempt to deal with varieties that may be linguistically distinct from each other, but are treated by their speakers as two forms of the same language, e.g. in cases of diglossia.
- http://www.sil.org/iso639-3/documentation.asp?id=ara (Generic Arabic, 639-2)
- http://www.sil.org/iso639-3/documentation.asp?id=arb (Standard Arabic, 639-3)
See  for the complete list.
 Collective languages
Some ISO 639-2 codes that are commonly used for languages do not precisely represent a particular language or some related languages (as the above macrolanguages). They are regarded as collective languages (or collectives) and are excluded from ISO 639-3.
- See also: ISO 639-2#Collective languages
- 2006-07-14 FDIS 50.00
- 2007-02-05 60.60
 See also
- ^ a b ISO 639-3 status and abstract (iso.org)
- ^ ISO 639-3 Code Set
- ^ Scope of denotation: Macrolanguages (sil.org)
- ^ Macrolanguage Mappings (sil.org)
- ^ Scope of denotation: Collective languages (sil.org)