贵族指的是奴隶制、封建制、君主制、教会制、种姓制等国家和地区的一些特有的群体，通过血缘、姓氏等某种特有的制度来继承知识、权力、财富而形成的传统。通常贵族成员拥有的知识与道德水平高于其他人，权力与责任大于其他人，财富多于其他人。经过现代化的发展，一些国家和地区依然有完整的贵族传统。

贵族同其他阶级的最明显区别是拥有爵位，但拥有爵位的人不一定是贵族。贵族爵位的特点是世袭，拥有非世袭爵位的人一般不被认为是贵族而是官僚。反过来说仅拥有贵族血统但无爵位的话，有可能被看成仅是世族或士族。

Nobility is a social class, normally ranked immediately under royalty, that possesses more acknowledged privileges or eminence 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, occasionally or often, enabled commoners to ascend into the nobility.