Any spoken variety of a language. As a language changes, its dialects may diverge and eventually become separate languages (e.g., Spanish and French evolved from dialects of Latin). The point at which a dialect becomes a language cannot be determined precisely. Linguists use the criterion of mutual intelligibility (see below) to determine whether two language varieties are dialects of a single language or are distinct languages.
A language at risk of extinction. Signs that a language is endangered include a relatively small number of speakers, declining numbers of speakers, and speakers all above a certain age (that is, children are not learning the language).
The patterns by which language are formed. For linguists, what is grammatical is based on real world use: If a group of people use and understand a phrase, it is grammatical for their dialect. This differs from the traditional idea that there is only one 'correct' way to speak. In linguistics, only sentences that no native speaker would use are judged as ungrammatical (e.g., "John to went my over house").
A repository that safeguards recordings of languages in various media and makes them available to users.
When a community gradually stops using a language and no longer passes it on to their children. A 'dead' language that has been documented and recorded is sometimes termed a 'sleeping' language. These languages can be awakened or revived through revitalization efforts.
Recording of the linguistic and cultural information in a community.
Positive value placed on a language or features of a language. Often a language or a language variety is considered prestigious when it is spoken by those in power.
Actions and policies to promote and increase the use of a language, with the goal of stopping or reversing its decline.
An attempt to bring back a language that has already lost all its speakers, by teaching it to people who will become new speakers.
The most common process in a language's ceasing to be spoken. Speakers almost invariably shift from a small, local indigenous language to a national or global language. As speakers use the language of prestige (see language prestige) more often, they stop passing on the indigenous language to children. This leads to its demise.
The scientific study of language and an academic discipline taught at universities.
A language that will almost certainly become extinct in the near future because no children speak it as their first language. Languages like Chulym and Chemehuevi, with only a few elderly speakers, are moribund.
If speakers of two different language varieties can understand one another, their tongues are mutually intelligible and they are probably speaking different dialects of a single language. If two speakers are mutually unintelligible, then they are speaking two different languages.
The language or languages learned naturally in early childhood, also called first language. This is not always the same as an ancestral language or heritage language, terms which refer to a language that was spoken by a person's ancestors. For example, the heritage language of the Chulym youth is Chulym, but Russian is probably their native language.