Several events are commonly proposed to mark the transition from Republic to Empire, including Julius Caesar’s appointment as perpetual dictator in 44 BC, the victory of Octavian at the Battle of Actium on 2 September 31 BC, and the Roman Senate’s granting to Octavian the honorific Augustus on 4 January 27 BC.
The Latin term Imperium Romanum (Roman Empire), indicated any part of the world under Roman rule. Roman expansion began in the days of the Republic, but reached its zenith under Emperor Trajan. At this territorial peak, the Roman Empire controlled approximately 6,500,000 square kilometers of land surface. Because of the Empire’s vast extent and long endurance, Roman influence upon the language, religion, architecture, philosophy, law, and government of nations around the world lasts to this day.