A commissioned officer is a member of a military force who derives authority directly from a sovereign power, and as such holds a commission from that power.
Commissioned officers are authorized to use deadly force to carry out the lawful orders of their government, either directly or through orders to non-commissioned officers or soldiers.
Having officers is one requirement for combatant status under the laws of war.
In the United States, there are some commissioned officers who are not members of the military. See uniformed services of the United States, NOAA Corps, and United States Public Health Service.
British Commissioned Officer Ranks
Royal Air Force
US Commissioned Officer Ranks
Army / Air Force / Marine Corps
Navy / Coast Guard
- U.S. DoD Officer Rank Insignia (http://www.defenselink.mil/specials/insignias/officers.html)