Emperor

Emperor, title, the meaning of which is derived from the Latin imperator, which at first was applied generally to any magistrate of ancient Rome vested with power to command and to enforce the laws of the state. Later, the term came to be used specifically by Roman troops for a victorious general until the termination of his imperium (“command”) on returning to Rome. In the later Republic, the Senate, on occasion, would invite a victorious general to assume the title permanently. Rome was already an empire when Julius Caesar adopted the title; thus, imperator for the first time denoted a sovereign ruler, rather than merely a victorious commander. Augustus, the grandnephew of Julius Caesar, established the principle of prefixing the title to the first name; but this did not become a regular practice with Roman rulers until the reign of Nero in 54-68. In the 9th century, Charlemagne took the title, and later it was assumed by the sovereigns of the Holy Roman Empire.

Various states elsewhere in the world have had their sovereigns referred to, by analogy, as emperors. In imperial China, the emperor possessed an equivalent status to the sovereigns of imperial Rome. In Japan, the tenno (“heavenly sovereign”), styled emperor in the West after the example of China, historically held little real power and, as a semidivine sovereign of a single country, was closer in role to a priest-king.

The title emperor generally refers to a ruler of wide territories and peoples, whereas the title king applies to the ruler of a single territory and people. Throughout history various rulers have adopted the title of emperor, but with changes in the political structure of states and the granting of independence to many colonial possessions, the basis for the term is disappearing.