Nobility is a social class, normally ranked immediately under royalty, that possesses more acknowledged privileges or 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 of 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. Nonetheless, nobility per se has rarely constituted a closed caste; acquisition of sufficient power, wealth, military prowess or royal favour has, occasionally or often, enabled commoners to ascend into the nobility.