Give me 5 facts for oligarchy

The word “oligarchy” and the concepts which it symbolizes originated in ancient Greece. In its basic use, the word identified one of the general forms of government recognized by the Greeks: that in which political government is conducted by a few persons or families. It was also used more narrowly, by Aristotle for example, to refer to the debased form of aristocracy, that is, to government by the few or by a faction. The term “oligarchy” was also used to refer to the small group of persons who enjoyed a monopoly of political control in oligarchic governments; the term usually had the added sense that the oligarchy ruled in its own rather than in the public interest. For Aristotle, classification of governments rested on two independent variables: the number of persons who ruled and the purposes served by their rule. Oligarchy was present when a few persons ruled for their own satisfaction.