A tyrant (Greek τύραννος, tyrannos), in its modern English usage, is an absolute ruler unrestrained by law or person, or one who has usurped legitimate sovereignty. Often described as a cruel character, a tyrant defends his position by oppressive means, tending to control almost everything in the state. The original Greek term, however, merely meant an authoritarian sovereign without reference to character, bearing no pejorative connotation during the Archaic and early Classical periods. However, it was clearly a negative word to Plato, a Greek philosopher, and on account of the decisive influence of philosophy on politics, its negative connotations only increased, continuing into the Hellenistic period.
Plato and Aristotle define a tyrant as "one who rules without law, and uses extreme and cruel tactics—against his own people as well as others". It is defined further in the Encyclopédie as a usurper of sovereign power who makes his subjects the victims of his passions and unjust desires, which he substitutes for laws. During the seventh and sixth centuries BC, tyranny was often looked upon as an intermediate stage between narrow oligarchy and more democratic forms of polity. However, in the late fifth and fourth centuries BC, a new kind of tyrant, the military dictator, arose, specifically in Sicily.
Tyranny includes a variety of oppressive types of government - by a tyrant (autocracy), by a minority (oligarchy, tyranny of the minority) or by a majority (democracy, tyranny of the majority). The definition is extended to other oppressive leadership and to oppressive policies. For example a teacher may find the school administration, the textbook or standardized tests to be oppressive, considering each to represent a tyranny.
The English noun appears in Middle English use, via Old French, from the 1290s. The word derives from Latin tyrannus, meaning "illegitimate ruler", and this in turn from the Greek τύραννος tyrannos "monarch, ruler of a polis"; tyrannos in its turn has a Pre-Greek origin, perhaps from Lydian. The final -t arises in Old French by association with the present participles in -ant.