Classical Latin is the form of Literary Latin recognized as a literary standard by writers of the late Roman Republic and early Roman Empire. It developed around 75 BC from Old Latin, and developed by the 3rd century AD into Late Latin. In some later periods, the former was regarded as good or proper Latin, while the latter was seen as debased, degenerate, or corrupted. The word Latin is now understood by default to mean "Classical Latin"; for example, modern Latin textbooks almost exclusively teach Classical Latin.
Cicero and his contemporaries of the late republic referred to the Latin language, in contrast to other languages such as Greek, as lingua latina or sermo latinus. They distinguished the common vernacular, however, as Vulgar Latin (sermo vulgaris and sermo vulgi), in contrast to the higher register that they called latinitas, sometimes translated as "Latinity". Latinitas was also called sermo familiaris ("speech of the good families"), sermo urbanus ("speech of the city"), and in rare cases sermo nobilis ("noble speech"). Besides the noun Latinitas, it was referred to with the adverb latine ("in (good) Latin", literally "Latinly") or its comparative latinius ("in better Latin", literally "more Latinly").
