(of a person, institution, or written work) The quality or characteristic of being respected for having good character or knowledge, especially as a source of guidance or an exemplar of proper conduct.

Any authority which has a legal mandate to govern, administrate a part or aspect of public life, such as all branches of the executive power of a state, province, municipality etc.

(rhetoric) Deeming an assertion to be true because of the position or the authority of the person asserting it.

(Australia, New Zealand, UK, law) A body set up by law which is authorised to enforce legislation on behalf of the relevant country or state.

A government organization responsible for collecting taxes.

plural of appeal to authority

A public authority which operates a port or other transportation infrastructure.

(library science) The organization of bibliographic information by using a single distinct spelling of a name (heading) or a numeric identifier for each topic or agent.

Someone who is in a position of authority.

plural of authority figure