Latin also pops up on U.S. coins; the phrase "e pluribus unum" means "out of many, one"

Even though Latin is a "dead" language because it has ceased to evolve, millions of people study it in school. That's because Latin pops up in medicine and law and is the root of many Spanish, Portuguese, French, Romanian -- and English -- words.

So there's dead like "Latin dead" -- and REALLY dead: completely obliterated, like hundreds of the early languages of North America. Nobody, but nobody, speaks these tongues any more. That's because almost none of them were written, and also because some tribes disappeared entirely or adopted their region's dominant English or French. So the elders stopped handing down their language to the young.

But now there's work afoot to revive many of these dead languages, and not just for sheer academic pleasure. Revitalizing the old tongue is a matter of pride in some tribes. And it can come in handy, as when scholars were able to reconstruct enough of the long-dead Virginia Algonquian language that the native characters could speak it credibly in a movie called The New World.

But reviving an old, dead language is tough work, especially with no scrolls, no storybooks, no grammar lists -- no written language at all -- to go by. The experts must rely on the crude notes of European settlers, who took a stab at writing down a few Indian words as they heard them spoken, and spelled the words as they pleased.

The death of languages is not just an American problem. In a recent New York Times article, the Smithsonian Institution's Ives Goddard estimated that within a century -- without a concerted effort to save them and teach them to the young -- half the world's 6,000 surviving languages will be extinct. Or "mortuus," as we'd say in Latin, if we spoke it anymore.