oligarchy vs. monarchy

noun

plural

oligarchies 
  1. a form of government in which all power is vested in a few persons or in a dominant class or clique; government by the few.

  2. a state or organization so ruled.

  3. the persons or class so ruling.

noun

plural

monarchies 
  1. a state or nation in which the supreme power is actually or nominally lodged in a monarch.

  2. supreme power or sovereignty held by a single person.