person who is enlisted in a branch of the armed force
United States Armed Forces oath of enlistment Upon enlisting in the United States Armed Forces, each person enlisting in an armed force (whether a soldier, sailor, coast guardsman, airman, or Marine) takes an oath of enlistment required by federal statute in 10 U.S.C. § 502. That section provides the text of the oath and sets out who may administer the oath:
Military rank "The [U.S.] commissioned officer corps is divided into 10 pay grades (O-1 through O-10). Officers in pay grades O-1 through O-3 are considered company grade officers. In the Army, Marine Corps, and Air Force, these pay grades correspond to the ranks of second lieutenant (O-1), first lieutenant (O-2), and captain (O-3), and in the Navy, ensign, lieutenant junior grade, and lieutenant. Officers in the next three pay grades (O-4 through O-6) are considered field grade officers. In the Army, Marine Corps, and Air Force, these pay grades correspond to the ranks of major (O-4), lieutenant colonel (O-5), and colonel (O-6), and in the Navy, lieutenant commander, commander, and captain. The highest four pay grades are reserved for general officers in the Army, Marine Corps, and Air Force, and flag officers in the Navy. The ranks associated with each pay grade are as follows: in the Army, Marine Corps, and Air Force, brigadier general (O-7), major general (O-8), lieutenant general (O-9), and general (O-10); in the Navy, rear admiral-lower half, rear admiral-upper half, vice admiral, and admiral."[10][11]