What is the definition of "rare language"?

Question

The term "rare languages" is sometimes used in newspaper headings, blog posts, etc. For example:

• This Innovative Platform Ensures That Kids in India Have Access to Stories in Their Mother Tongue, The Better India, 26 Jul 2016 (examples: Sanskrit, Banjari, Lambadi, Kuruk, Oraon, Gondi, Mundari, Sadri, Santhali and Kora),
• Preserve rare languages to spread benefits of multilingualism, says expert, The Guardian, 15 Feb 2016 (examples: Sardinian and Scottish Gaelic),
• Economic success 'drives language extinction', BBC News, 3 Sep 2014 (examples: Upper Tanana, Ume Sami, Auvergnat, Bahing),
• For Rare Languages, Social Media Provide New Hope, NPR, 26 Jul 2014 (examples: Aymara, Tongva, Anishinaabemowin),
• About 2,000 rare languages may disappear on Earth in 100 years, PravdaReport, 29 Nov 2007 (examples: Siletz Dee-ni, which had only one speaker at the time),
• Top Five Rarest Languages, Network Languages Ltd, 10 Mar 2014 (Njerep, Chemehuevi, Kaixana or Caixana, Taushiro or Pinche, Liki).

When you actually read the articles, they are usually about endangered languages. So my question is: Do linguists use a definition of rare language that is different from "endangered language"? (That is, if they actually use the term "rare language".)

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PS: There appears to be no agreed-upon definition of endangered or threatened language. The abstract of this article says that

(...) languages have been classified as threatened if the number of speakers is less than 100, 500, 1,000, 10,000, 20,000 or 100,000 (...).

UNESCO uses nine factors to determine whether a language is endangered.

Update: Not all "rare" languages are endangered. In a PBS documentary, the poet Bob Holman says that he visited one of the Goulburn Islands, where there were 400 people and 10 different languages. In spite of a small number of speakers, some of the rare languages in Australia are stable because people don't find it a big deal to learn other languages, and learning the language of another people is a sign of respect.

Answer 1

The articles you've linked to weren't written by linguists. I don't think "rare language" is an established term in linguistics. If it's used in a professional or academic context, it needs to be defined beforehand. For example, the National Register for Public Service Interpreters in the UK defines a "rare language" as follows:

Recognition is given to the fact that there are so called ‘rare languages’ where the chance to establish assessment opportunities is outstripped by demand for the language. [...] Limited assessment and rare language categories deal with the practical realities of situations where a nationally recognised examination in a particular language is not yet available, or such an examination has not yet been taken or where the applicant has passed a test for working in, for example, immigration services.

In other words, a "rare language" according to NRPSI is any language that doesn't have a nationally recognised exam. But this is just a definition that was useful for this particular institution.

Answer 2

"Rare languages" is not a term that is used by linguists, and it does not have any real meaning. It is a phrase that is often used by the writers of newspaper headlines, presumably because it is shorter than "endangered languages", in the same way that they like to write "poll" when they mean "election". "Top Five Rarest Languages", if it means anything, should mean the five languages with the smallest number of speakers.

Answer 3

I think rare language is not a linguistic term.

There are several aspects that can make a language rare in some sense

• Being endangered (on the verge of extinction)
• Having few speakers (which is not necessarily the same as the above)
• Being under-resourced, i.e., having little available documentation and/or resources

Often, the aspects of rareness occur together, but this is not necessarily the case. A thriving language of Africa can still be under-resourced, and we have well-documented dead languages. A language with a few speakers in some part of the world may be not endangered, yet another one with more than a million speakers in another part of the world may be critically endangered.