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(1) The name for a monarchical state headed by an emperor. An empire is most often a vast state that has incorporated, usually by conquest, the territory of other peoples and states. Some empires included several kingdoms. The Roman state was called an empire after Augustus established the individual power of the emperor in the late first century B.C. Later empires included Byzantium; the Frankish state under Charlemagne, who adopted the title of emperor in 800; and the medieval Holy Roman Empire. Tsarist Russia was an empire from the time of Peter I (1721) until the overthrow of the monarchy in 1917. Other examples of empires are bourgeois France under Napoleon I (the First Empire) and Napoleon III (the Second Empire), Austria from 1804 (Austria-Hungary from 1868) until 1918, and Germany from 1871 until the revolution of 1918.
(2) Large states that have vast colonial possessions. The empire consists of the mother country and its colonies—for example, the British empire included Great Britain and all of its dominions and colonies.