began = 27 BC
ended = 476 ADThe Roman Empire is a phase of the ancient Roman civilization characterized by an autocratic form of government and large territorial holdings in Europe and around the Mediterranean. The Roman Empire is considered to have begun with the creation of the Principate in 27 BC when Augustus began skillfully centralizing power, bringing an end to the Republic of Rome in fact but not appearance. Roman citizens would go on considering themselves under a republic for another 300 years.
The Latin term “Imperium Romanum” (Roman Empire), the best-known Latin expression was the word “imperium” denotes a territory known as homoland, indicates the part of the world under Roman rule. Roman expansion began in the days of the Republic with their war with Carthage, but reached its zenith under Emperor Trajan. At this territorial peak, the Roman Empire controlled approximately 5,900,000 km² (2,300,000 sq mi) of the earth’s surface.cite web