An emperor (through Old French empereor from Latin: 'imperator') is a monarch, usually the sovereign ruler of an empire or another type of imperial realm. Empress, the female equivalent, may indicate an emperor's wife (empress consort), mother (empress dowager), or a woman who rules in her own right (empress regnant). Emperors are generally recognized to be of a higher honour and rank than kings. In Europe the title of Emperor was, since the Middle Ages, considered 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 Western Europe. The Emperor of Japan is the only currently reigning monarch whose title is translated into English as "Emperor".
Both kings and emperors are monarchs, but emperor and empress are considered the higher monarchical titles. Inasmuch as there is a strict definition of emperor, it is that an emperor has no relations implying the superiority of any other ruler, and typically rules over more than one nation. Thus a king might be obliged to pay tribute to another ruler, or be restrained in his actions in some unequal fashion, but an emperor should in theory be completely free of such restraints. However monarchs heading empires have not always used the title—the British sovereign did not assume the title until the incorporation of India into the British Empire, and used it to symbolise British control over all its territories, even those lying outside actual British India, the reason being that India was the jewel in the crown of the British Empire. Similarly before the 19th century the term Emperor in Europe referred exclusively to the Holy Roman Emperor, despite the fact that the empire neither contained Rome nor did it exercise much power beyond the German speaking states, by the late 16th century the empire itself came to mean the dynastic lands held by the Habsburgs and following the Thirty Years' War the Habsburg emperors control over the German states outside Habsburg Austria became nearly non-existent, the position of Emperor however continued till the early 19th century, before it was abolished by Francis II who became the first Emperor of Austria. For purposes of protocol, emperors were once given precedence over kings in international diplomatic relations; currently, however, precedence amongst heads of state – whether they be Kings, Queens, Emperors, or Presidents – is determined by the duration of time that each one has been continuously in office.
Outside the European context, emperor was the translation given to holders of titles who were accorded the same precedence as European emperors in diplomatic terms. In reciprocity, these rulers might accredit equal titles in their native languages to their European peers. Through centuries of international convention, this has become the dominant rule to identifying an emperor in the modern era.
Some empires, such as the Holy Roman Empire and the Russian Empire, derived their office from the authority of the Roman Emperors (translatio imperii). The title was a conscious attempt by monarchs to link themselves to the institutions and traditions of the Romans as part of state ideology. Historians have liberally used emperor and empire anachronistically and out of its Roman and European context to describe any large state from the past or the present. Such pre-Roman titles as "Great King" or "King of Kings", used by the Kings of Persia and others, are often considered as the equivalent. Sometimes this reference has even extended to non-monarchically ruled states and their spheres of influence such as the "Athenian Empire" of the late 5th century BC, the "Angevin Empire" of the Plantagenets, the Soviet, and American "empires" of the Cold War era. However such "empires" did not need to be headed by an "emperor". Empire became identified instead with vast territorial holdings rather than the title of its ruler by the mid-18th century....LESS