Classical Latin is the form of 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.