means A form of government in which a single person, usually a king or queen, holds supreme power, typically inheriting the role and keeping it for life.

from From Greek 'monarkhia,' a marriage of 'monos' (alone, single) and 'arkhein' (to rule) — literally 'rule by one.' That same 'arkhein' fathered a whole family of power-words: anarchy (no rule), oligarchy (rule by a few), hierarchy (sacred rule). It strolled into Latin as 'monarchia,' through Old French, and into English in the late Middle Ages, where the one who did the ruling was, fittingly, the monarch.