Military members who are currently serving full-time in their military capacity. Members of a reserve component may be "called up" to serve on active duty.

Members generally perform a minimum of 39 days of military duty per year and augment the active duty military forces when necessary. Reserve Units (in every branch of the military) are commanded at the federal level and the general purpose is to provide trained units in time of war or other national emergency. Army National Guard and Air National Guard are generally commanded at the state level by governors, and called to active duty in response to domestic emergencies and disasters.

A person who is currently serving in the United States Armed Forces. Reserve and National Guard military personnel are considered service member as well.

A person who has served in the United States Armed Forces. Another term used is "former armed services personnel". The United States Armed Forces consist of the branches of the Army, Navy, Marine Corps, Air Force, and Coast Guard. A veteran could also have served in a National Guard unit.