changes in Latin from the Late Republic to Justini

"Classical" Latin, a preserved dialect of an otherwise constantly evolving language, would have continued to be taught with the aid of classical authors like Virigil and Cicero.  The Byzantine court continued to be an island of Latin in an otherwise Greek speaking world. Latin continued to be spoken as a "high" language in the West well into the Middle Ages. Charlemagne, for example, was a fluent speaker of Latin. Latin, with some changes in pronunciation, continued to be used for curial and ecclesiastical purposes up into the high Middle Ages. For example, in England the transcripts of court cases, which were held in French, were transcribed into Latin for the the record. Some Medievalists have argued the black death may have been a turning point for medieval Latinity, killing off so many grammarians and Latin teachers that a new generation of bureaucrats and nobles emerged who spoke only the venacular. Ironically, the Renaissance, which saw the rebirth of classical scholarship, marks a low point in the practical usage of Latin.

However, Latin itself was always evolving, even as the Romans spoke it--and we should see the transformation of Latin into the Romance languages as a remarkable evolution rather than a lamentable extinction.