Leid loss 
Normally the transition frae a dead tae an extinct leid occurs when a leid undergoes leid daith while being directly replaced bi a different ane. For example, Native American leids wur replaced bi Inglis, French, Portuguese, or Spainyie as a result o colonization. The Coptic leid, replaced bi Arabic in its native Egyp, wis ance thought to be extinct.
By contrast to an extinct language which no longer haes any speakers, a dead leid may remain in uise for scientific, legal, or ecclesiastical functions. Old Church Slavonic, Avestan, Coptic, Biblical Hebrew, Ge'ez, Latin, an Sanskrit ar among the mony dead leids usied as sacred leids.
Alternatively, a leid is said tae be extinct if, although it is known tae have been spoken bi fowk in the past, modern scholarship cannot reconstruct it tae the point that it is possible tae write in it or translate into it wi confidence (say, a simple dialogue or a short tale written in a modern leid); whereas a language is referred tae as dead, but not extinct, if it is sufficiently known at present tae permit such routine uise, even though it haes no modern speakers. Bi these definitions Proto-Indo-European (o which only conjectural reconstructions o lexicon an grammar exist) is an extinct leid, an Classical Latin an Old Tupi are dead, but not extinct leids.
Hebrew is an example o a nearly extinct spoken leid (bi the first definition 'boon) that became a lingua franca an a liturgical leid that haes been revived tae become a livin spoken leid. There ar other attempts at leid revival. For example, young school children uise Sanskrit in revived leid in Mathoor village (Indie). In general, the success o these attempts haes been subject tae debate, as it is not clear they will ever become the common native leid o a community o speakers.
It is believed that 90% o the circa 7,000 leids currently spoken in the warld will hae become extinct bi 2050, as the warld's leid system haes reached a crisis an is dramatically restructurin.
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