No inherited verbal knowledge of the ancient pronunciation of Latin exists. It must be reconstructed. Among the data used for reconstruction listed by Allen are explicit statements by ancient authors, especially grammarians, about the pronunciation of a word, puns, ancient etymologies, Latin words stated in other languages, and so on.
As with any language, pronunciation varied according to historical period. Standard practice in Latin education is to teach the pronunciation of classical Latin first. Most Latinists know the opening words of De Bello Gallico, Gallia est omnis divisa in partes tres ... and know that divisa is nowadays most often pronounced as "diwisa". It makes little difference whether the refrain of Oh come all ye faithful is sung as "venite, venite" or "wenite, wenite", although the first is more appropriate to the period. Period differences are generally taught with the works of their authors; however, the classical pronunciation is always generally acceptable.
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