Overview
An officer is a person who holds a position of authority as a member of an armed force or uniformed service.
Broadly speaking, "officer" means a commissioned officer, a non-commissioned officer (NCO), or a warrant officer. However, absent contextual qualification, the term typically refers only to a force's commissioned officers, the more senior members who derive their authority from a commission from the head of state.
Numbers
The proportion of officers varies greatly. Commissioned officers typically make up between an eighth and a fifth of modern armed forces personnel. In 2013, officers were the senior 17% of the British armed forces, and the senior 13.7% of the French armed forces. In 2012, officers made up about 18% of the German armed forces, and about 17.2% of the United States armed forces.
From Wikipedia (CC BY-SA 4.0).