In modern usage, a tyrant is a single ruler holding absolute power over a state or within an organization. The term carries modern connotations of a harsh and cruel ruler who places his or her own interests or the interests of a small oligarchy over the best interests of the general population which the tyrant governs or controls. However, in the classical sense, the word simply means one who has taken power by their own means as opposed to hereditary or constitutional power (and generally without the modern connotations). This mode of rule is referred to as tyranny. Many individual rulers or government officials are accused of tyranny, with the label almost always a matter of controversy.
The word derives from Latin tyrannus meaning "illegitimate ruler", and ultimately from Greek τύραννος tyrannos, meaning "sovereign, master", although the latter was not pejorative and applicable to both good and bad leaders alike.
In ancient Greece, tyrants were influential opportunists that came to power by securing the support of different factions of a deme. The word "tyrant" then carried no ethical censure; it simply referred to anyone who illegally seized executive power in a polis to engage in autocratic, though perhaps benevolent, government, or leadership in a crisis. Support for the tyrants came from the growing class of business people and from the peasants who had no land or were in debt to the wealthy land owners. It is true that they had no legal right to rule, but the people preferred them over kings or the aristocracy. The Greek tyrants stayed in power by using mercenary soldiers from outside of their respective city state. ,