Can a dead language come back to life?

Yes, but it has fully happened only once. Hebrew had not been anyone's mother tongue since the 2nd century CE, surviving for prayer and writing. Today it has several million native speakers. No other language with no native speakers has ever made that comeback. Efforts to rescue languages that are fading, or to wake up ones that have fallen silent, are called language revitalization.

The human story starts with one stubborn family. On 13 October 1881, in Paris, Eliezer Ben-Yehuda began speaking Hebrew with friends, in what is believed to be the first modern conversation in the language. Moving to Jerusalem, he decided his household would speak nothing but Hebrew. His son Itamar Ben-Avi, born in 1882, became the first native speaker of Modern Hebrew. Ben-Yehuda also invented many words for things the ancient language never needed, such as ḥashmal for electricity.

One family wasn't enough, though. What finally brought Hebrew back were the new Jewish settlements, where the first Hebrew schools were founded and children were raised fully immersed in the language. That same ingredient, children growing up inside the language, is behind one of the best partial successes elsewhere: Māori in New Zealand, whose preschool language nests began in the 1970s, more than a century after a law banned Māori in schools.

Revived languages don't come back unchanged. Modern Hebrew absorbed features from Yiddish and other languages, and some linguists argue that revived Hawaiian, shaped heavily by English, is really a new language.