The Ethnologue contains statistics for 6,912 languages in the 15th edition, released in 2005 (up from 6,809 in the 14th edition, released 2000) and gives the number of speakers, location, dialects, linguistic affiliations, availability of the Bible, and so forth. It is currently the most comprehensive existing language inventory, along with the Linguasphere Register. However, some information regarding more esoteric languages is quite dated.
What counts as a language depends on socio-linguistic evaluation: see Dialect. Some accuse the Ethnologue of dividing languages, preferring to call the different varieties "dialects". In other cases, the Ethnologue has been accused of lumping together different languages as "dialects" of single languages. As the preface says, "Not all scholars share the same set of criteria for what constitutes a 'language' and what features define a 'dialect.'"
In 1984 the Ethnologue released a three-letter coding system, called SIL code, to identify each language it describes. This set of codes significantly exceeded the scope of previous standards, e.g., ISO 639-1. The 14th edition, published in 2000, included 7148 language codes which generally did not match the ISO 639-2 codes. In 2002 the Ethnologue was asked to work with the International Organization for Standardization (ISO) to integrate its codes into a draft international standard. The Ethnologue now uses this standard, called ISO 639-3. The 15th edition which was published in 2005 includes 7299 codes. A 16th edition will be released early 2009.
In addition to choosing a primary name for the language, it also gives some of the names by which a language is called by its speakers, by the government, by foreigners, and by neighbors, as well as how it has been named and referenced historically, regardless of which designation is considered official, politically correct, or offensive, or by whom. This selection of "alternative names" is extensive, but often incomplete.
Ethnologue contains its fair share of errors. Some of the errors are fixed in every new edition; for instance, en route to the 14th edition, some languages such as Chenoua were added, and some rumoured "languages" such as Nemadi or Wutana were removed. Some possible remaining errors are discussed at Imraguen language, Senhaja de Srair language, Ghomara language, Kwavi language, Molengue language, Yauma language, Fer language, Yeni language, Hwla language, and Ofayé.
Bill Bright, editor of Language: Journal of the Linguistic Society of America, wrote that it "is indispensable for any reference shelf on the languages of the world" (1986:698).