language with only 500 speakers might be considered very much alive if it is the primary language of a community, and is the first (or only) spoken language of all children in that community.

Asserting that "Language diversity is essential to the human heritage", UNESCO's Ad Hoc Expert Group on Endangered Languages offers this definition of an endangered language: "... when its speakers cease to use it, use it in an increasingly reduced number of communicative domains, and cease to pass it on from one generation to the next. That is,