A person duly authorized by an officer to serve as his or her substitute by performing some or all of the officer's functions.
A deputy sheriff is designated to act on behalf of the sheriff in regard to official business.
A general deputy or undersheriff, pursuant to an appointment, has authority to execute all of the regular duties of the office of sheriff and serves process without any special authority from the sheriff.
A special deputy, who is an officer pro hac vice (Latin for "for this turn"), is appointed to render a special service. A special deputy acts under a specific, rather than a general, appointment and authority.