An emperor is a monarch, and usually the sovereign ruler of an empire or another type of imperial realm. Empress, the female equivalent, may indicate an emperor's wife, mother, or a woman who rules in her own right. Emperors are generally recognized to be of the highest monarchic honour and rank, surpassing kings. In Europe, the title of Emperor has been used since the Middle Ages, considered in those times equal or almost equal in dignity to that of Pope due to the latter's position as visible head of the Church and spiritual leader of the Catholic part of Western Europe. The Emperor of Japan is the only currently reigning monarch whose title is translated into English as "Emperor", although he holds no actual political power, nor is Japan an empire.