Relationship between ISO 639-3 and the other parts of ISO 639


Registration Authorities for the other parts of ISO 639

Relationships between Parts 1, 2 and 3

ISO 639 provides three language code sets: one is a two-letter code (ISO 639-1) and two others are three-letter codes (ISO 639-2 and ISO 639-3) for the representation of names of languages. ISO 639-1 was devised primarily for use in terminology, lexicography and linguistics. ISO 639-2 was devised primarily for use in terminology and bibliography. It represents all languages contained in ISO 639-1 and in addition other languages and language collections of interest for those primary applications. ISO 639-3 was devised to provide a comprehensive set of identifiers for all languages for use in a wide range of applications, including linguistics, lexicography and internationalization of information systems. It attempts to represent all known full languages.

The three-letter codes in ISO 639-2 and ISO 639-3 are complementary and compatible. The two codes have been devised for different purposes. The set of individual languages listed in ISO 639-2 is a subset of those listed in ISO 639-3. The codes differ in that ISO 639-2 includes code elements representing some individual languages and also collections of languages, while ISO 639-3 includes code elements for all known individual languages but not for collections of languages. Overall, the set of individual languages listed in ISO 639-3 is much larger than the set of individual languages listed in ISO 639-2.

The languages represented in ISO 639-1 are a subset of those represented in ISO 639-2; every language code element in the two-letter code has a corresponding language code element in ISO 639-2, but not vice versa. In the same way, elements other than collections listed in ISO 639-2 are a subset of those listed ISO 639-3; each non-collective element in ISO 639-2 is generally included in ISO 639-3, but not vice versa. The denotation represented by alpha-3 identifiers included in both ISO 639-2 and ISO 639-3 is the same in each standard, and the denotation represented by alpha-2 identifiers in ISO 639-1 is the same as that represented by the corresponding alpha-3 identifiers in ISO 639-2 and ISO 639-3.

The language identifiers in ISO 639-3 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 attempts to provide as complete an enumeration of languages as possible, including living, extinct, ancient and constructed languages, whether major or minor. As a result, ISO 639-3 lists 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. Constructed languages that have not come into general use beyond a generation are also excluded.

The alpha-3 codes for ISO 639-2 and ISO 639-3 overlap. In particular, every individual language code element in the terminology code of ISO 639-2 is also included in ISO 639-3. One is not a subset of the other, however: the collective language code elements in ISO 639-2 have no counterpart in ISO 639-3, and there are many individual language code elements in ISO 639-3 that have no counterpart in ISO 639-2. The alpha-3 identifiers for these two non-intersecting sets of code elements are guaranteed to be distinct; that is, every alpha-3 language identifier has a single denotation across the union of code elements from all parts of ISO 639.

Some existing code elements in ISO 639-2, and the corresponding code elements in ISO 639-1, are designated in those parts of ISO 639 as individual language code elements, yet are in a one-to-many relationship with individual language code elements in this part of ISO 639. For purposes of this part of ISO 639, they are considered to be macrolanguage code elements.

In certain cases, a macrolanguage code element in ISO 639-1 or ISO 639-2 may have the same name as one of the individual languages in ISO 639-3 that falls within its scope. In order to preserve unique names within ISO 639-3, the qualifier "(macrolanguage)" is added to the name for the macrolanguage code element when listed in the code tables for ISO 639-3. This does not imply any change to the name within any other part of ISO 639. Similarly, the qualifier "(individual language)" is added to the name for the corresponding individual language code element.

ISO 639-2 includes two code sets, a terminology code and a bibliographic code, that differ in the identifiers used to represent certain languages. These are designated as 639-2(T) and 639-2(B), respectively. In a small number of cases, a given language is assigned a terminology-code language identifier and a distinct bibliographic-code language identifier. The corresponding code elements in ISO 639-3 use the terminology-code identifier from ISO 639-2; no bibliographic-code language identifier from ISO 639-2 is used in ISO 639-3. The assignment of distinct bibliographic-code identifiers in ISO 639-2 has no impact on ISO 639-3 except for the need to co-ordinate the use of alpha-3 identifiers such that identifiers for bibliographic code elements in ISO 639-2 are not used as identifiers for any code element in ISO 639-3.

Collective code elements, Parts 2 and 5

ISO 639-5, Codes for the representation of names of languages--Part 5: Alpha-3 code for language families and groups, contains collective language code elements for language families or geographic groupings of languages. It also shares the three-letter alphabetic code space of Parts 2 and 3. Part 5 contains all the collective language code elements of Part 2, and many additional code elements. The code elements of Part 5 are included in the Part 2/Part 5 code element sort and the Name sort views of the Language Codes pages, with links to individual documentation pages. However, as with Parts 1 and 2, these pages are not to be considered authoritative with regard to their respective code sets. They are included for informational purposes only. Part 5 code elements are not included in the downloadable code tables.

The existence of collective language code elements in ISO 639-2 and ISO 639-5 has no impact on ISO 639-3 except for the need to co-ordinate the use of alpha-3 identifiers such that identifiers for collective language code elements are not used as identifiers for any code element in ISO 639-3. Thus, every alpha-3 language identifier has a single denotation across the union of code elements from all parts of ISO 639.