An emperor (through Old French empereor from Latin imperator) is a (male) 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) or a woman who rules in her own right (empress regnant). Emperors are generally recognized to be of a higher honor and rank than kings.
Currently, the Emperor of Japan is the only reigning monarch with the title.
Distinction from other monarchs
Both kings and emperors are monarchs. Within the European context, "emperor" and "empress" are considered the higher monarchical titles. Emperors were once given precedence over kings in international diplomatic relations; currently, precedence is decided by the length a head of state is continuously in office.
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. Similarly, many republics have named a legislative chamber after the Roman Senate.
Historians have liberally used "emperor" and "empire" anachronistically and out of its Roman and European context to describe any large state and its ruler in the past and present. "Empire" became identified with vast territorial holdings rather than the title of its ruler by the mid-18th century.