I was catching up on my Omniglot Blog unread posts and I came across this post asking people When is a language dead? This whole discussion come up because Manx was declared as a dead language even though there are still speakers of the language.

The range of opinions posted in the comments was quite interesting, and it serves to point out there is not consensus on when a language is dead, or in some cases rather remains dead.

View 1: A language is dead when there are are no monolingual speakers of that language.
I find this line of logic to be wrong. Back when movement across country lines and continents meant long journeys, often expensive, this may have been a good indicator because a lot of people were monolingual. In these days bilingualism (or multilingualism) is the norm. In areas where there is a common language, or history of subjugation, its common to find the language of the conqueror taught first and then the native language. As we move into a more connected world, monolingualism will be more or less a thing of the past, or for countries like the US who are so vast that they do not see the reason to learn a foreign language.

View 2: A language is dead, even if it can be revived, it's still dead because it's no longer used or pronounced in the same way as it was before (example: ancient Greek, and Latin). What I find interesting about this argument is that English itself has evolved. We don't consider middle English or Old English dead, we just consider them as older forms of the language we use now. In addition, English had the "great vowel shift" which changed how things were pronounced. Does this mean that that English is dead and the one that we speak now is not? I see language as a continuum, and I think most linguists do as well. I don't think that there are hard cut off periods or incidents when a language is considered dead.

In my opinion a language is dead when no one speaks it any longer and there is no way to get it back because no one has recorded it. So long as there are records of a language and there is a concerted effort to revive it and get people speaking it, a language that was dead can be revived. The issue of convenience or "why are we learning X when we can just as well use English" is a whole other issue.