병사(兵士) means "soldier", general word for soldier 사병(士兵) means "soldier, "more specifically ranks, ranker" i.e. the antonym of 장교(將校)(officer) 전사(戰士) means "warrior" , used for ancient soldier or figuratively like 태극전사(the Korean national soccer team),산업전사(an industrial worker) 용사(勇士) means "soldier, warrior", formal word for soldier, literal meaning is "brave soldier"용감한 병사 군인(軍人) means "serviceperson" including all kind of military service like soldier, officer, marine, navy man, airman i.e. the antonym of 민간인(civilian) 무사(武士) means "warrior", used only for ancient warrior