What are endangered languages?

How do researchers know when a language is dying? Does "endangered" mean "doomed?"

Many factors contribute to a language becoming endangered. SIL makes concerted efforts to survey languages, evaluate their vitality, facilitate language development, and where possible, support members of the speech community in their desire to document and maintain their language and culture.

The danger of languages dying out is real, and SIL believes every language and culture is part of the mosaic of humanity. SIL is concerned for languages, the people who speak them, and the cultures they express.