A combatant is a person who takes a direct part in the hostilities of an armed conflict. If a combatant follows the law of war, then he or she is considered a privileged combatant and upon capture, he or she will qualify as a prisoner of war under the Third Geneva Convention (GCIII). An unprivileged combatant is a person, such as a mercenary, who takes a direct part in the hostilities but who upon capture does not qualify for prisoner-of-war status. (source)