Nobility is a social class, normally ranked immediately under royalty, that possesses more acknowledged privileges and higher social status than most other classes in a society, membership thereof typically being hereditary. The privileges associated with nobility may constitute substantial advantages over or relative to non-nobles, or may be largely honorary (e.g., precedence), and vary from country to country and era to era. Historically, membership in the nobility and the prerogatives thereof have been regulated or acknowledged by the monarch or government, thereby distinguishing it from other sectors of a nation's upper class wherein wealth, lifestyle or affiliation may be the salient markers of membership. Nonetheless, nobility per se has rarely constituted a closed caste; acquisition of sufficient power, wealth, military prowess or royal favour has, with varying frequency, enabled commoners to ascend into the nobility.
There is often a variety of ranks within the noble class. Legal recognition of nobility has been more common in monarchies, but nobility also existed in such regimes as the Dutch Republic (1581–1795), the Republic of Genoa (1005–1815) and the Republic of Venice (697–1797), and remains part of the legal social structure of some non-hereditary regimes, e.g., San Marino and the Vatican City in Europe. Hereditary titles often distinguish nobles from non-nobles, although in many nations most of the nobility have been un-titled, and a hereditary title need not ipso facto indicate nobility (e.g., vidame). Some countries have had non-hereditary nobility, such as the Empire of Brazil.
The term derives from Latin nobilitas, the abstract noun of the adjective nobilis ("well-known, famous, notable"). In ancient Roman society, nobiles originated as an informal designation for the political governing class who had allied interests, including both patricians and plebeian families (gentes) with an ancestor who had risen to the consulship through his own merit (see novus homo, "new man").