An emperor (female equivalent: empress ) is a male who rules an empire . The word is taken from the Latin language Imperator . Often it is capitalized .

A woman who comes to power in an empire is called an empress. The wife of an emperor is also called an empress. An emperor or empress is often a hereditary monarch and comes to power when one of his parents, or relatives , dies . In some countries, people elected a new emperor from candidates .

The only emperor in the world today is the Emperor of Japan ( tenn? ), but he lacks political power. The true leaders of Japan are the Diet and Prime Minister because the country is a parliamentary constitutional monarchy .

The English word comes from Latin , the language of the old Roman Empire . At first, an imperator was a powerful general (army leader) but, after Augustus , it was only used by their most powerful rulers . There have been many countries in history whose leaders are called "emperors" in English. The leaders of the Byzantine Empire ( basileus , Autokrator ) in Greece , the Holy Roman Empire ( imperator , Kaiser ) in Austria and Germany , Russian Empire , Serbia , and Bulgaria ( tsar ), and the Ottoman Empire ( sultan , padishah , khagan , kaysar ) in Turkey all said they were just new parts of the old Roman Empire .

The leaders of other countries who said they ruled the whole world or called themselves " King of Kings " are frequently also called emperors in English . For example, the old rulers of China ( Huangdi ), Iran ( Shah ), and Ethiopia ( Negusa negast ) are all known as emperors in English . There have also been emperors of France , Brazil , and Mexico , and the rulers of the United Kingdom called themselves the Emperors and empresses of India for a while.