The aristocracy is historically associated with "hereditary" or "ruling" social class. In many states, the aristocracy included the upper class of people (aristocrats) with hereditary rank and titles. In some, such as ancient Greece, ancient Rome, or India, aristocratic status came from belonging to a military caste. It has also been common, notably in African societies, for aristocrats to belong to priestly dynasties. Aristocratic status can involve feudal or legal privileges. They are usually below only the monarch of a country or nation in its social hierarchy. In modern European societies, the aristocracy has often coincided with the nobility, a specific class that arose in the Middle Ages, but the term "aristocracy" is sometimes also applied to other elites, and is used as a more generic term when describing earlier and non-European societies. Some revolutions, such as the French Revolution, have been followed by the abolition of the aristocracy.
The term aristokratia was first used in Athens with reference to young citizens (the men of the ruling class) who led armies at the front line. Aristokratia roughly translates to "rule of the best born". Due to martial bravery being highly regarded as a virtue in ancient Greece, it was assumed that the armies were being led by "the best". This virtue was called arete (). Etymologically, as the word developed, it also produced a more political term: aristoi (?). The term aristocracy is a compound word stemming from the singular of aristoi, aristos (?), and the Greek word for power, kratos ().
From the ancient Greeks, the term passed to the European Middle Ages for a similar hereditary class of military leaders, often referred to as the nobility. As in Greece, this was a class of privileged men and women whose familial connections to the regional armies allowed them to present themselves as the most "noble" or "best" of society.