Emperor is the ruler of an empire, or group of nations or states. A king usually rules only one area or people, but an emperor rules several. The word comes from the Latin word imperator, meaning commander. Emperor represented a military command in early Roman times, but later came to be the title of a ruler. After the fall of the Roman Empire in the West, in A.D. 476, the title passed out of use in Europe for several hundred years. In A.D. 800, Charlemagne had himself crowned emperor of the Romans. Since 1800, emperors have ruled China, France, Germany, Japan, and Russia at one time or another. The wife of an emperor or a woman who rules an empire is called an empress. See also Empire.