Authority is the official permission or right to act, often on behalf of another. Authority may also be a person or institution that has power over another person.
Authority as agency is the power to act on behalf of another; the power delegated by a principal to an agent. Authority is central to the law of agency—if someone takes an action on behalf of another without the authority to do so, the action is usually void. Actions carried out beyond or outside the scope of one’s authority are ultra vires (beyond the powers).
In the context of agency, authority may either be actual or implied/apparent/constructive. Actual authority is expressly or explicitly delegated by a principal to an agent. Implied authority, on the other hand, is not expressly delegated; instead, it is circumstantially inferred that the principal is meant to confer this authority upon the agent.
[Last updated in June of 2021 by the Wex Definitions Team]