Officer : a person holding a position of authority, especially one with a commission, in the armed services, the mercantile marine, or on a passenger ship.
Participant : a person who takes part in something.
Member : a person, animal, or plant belonging to a particular group.
Representative : typical of a class, group, or body of opinion.
Delegate : a person sent or authorized to represent others, in particular an elected representative sent to a conference.
Synonym of
Delegate is
Representative