An emperor is the male leader of an empire. Empress is the feminine form and can refer to a woman who holds the rank of emperor (empress regnant), a wife of an emperor (empress consort), or a widow of an emperor (empress dowager). Emperor is the highest temporal title there is, outranking even king. The only emperor in the world today is Emperor Akihito of Japan. However, at the beginning of the 20th century, other countries had emperors, including Austria-Hungary, China, Germany, the Ottoman Empire, and Russia. The term Emperor itself is of Old French origin, derived from the title of the head of state during the Roman Republic and Roman Empire, Imperator, which roughly meant "Commander."
Equivalent terms in other languages, sometimes used in English, include Kaiser in German, Tsar (царь) in Russian, Kōtei (皇帝) in Chinese (which is itself a reference to the Yellow Emperor of Chinese mytho-historical tales), and Tennō (天皇) in Japanese. Although some of the titles, such as the German and Russian versions of Emperor, were named after Caesar, others, such as the Chinese and Japanese titles, had no such basis.
Emperor is also a species of penguin.