A warrant of attorney is a legal document that authorizes a person to act on behalf of a client, usually in legal proceedings. Synonyms for warrant of attorney include power of attorney, letter of attorney, or authority to act. These terms are used interchangeably in legal contexts. A power of attorney is a more general term that encompasses the broad authorization given to a person to act on behalf of another, regardless of the context. A letter of attorney is a more specific term that refers to a document that gives a person the authority to act as an attorney in a specific legal matter. Authority to act is a broad term that can also refer to authorizations in other contexts, such as financial or business matters.