A non-commissioned officer or noncommissioned officer (NCO, colloquially non-com or noncom) is a military officer who has not earned a commission. Such is also called sub-officer in some countries. Non-commissioned officers, in the English-speaking world, usually obtain their position of authority by promotion through the enlisted ranks. In contrast, commissioned officers hold higher ranks than NCOs, have more legal responsibilities, are paid more, and often have more non- military training such as a university diploma. Commissioned officers usually earn their commissions without having risen through the enlisted ranks. " Mustang " is a slang term in the United States Armed Forces used to refer to a commissioned officer who began his or her career as an enlisted service member.
The NCO corps usually includes all grades of corporal and sergeant; in some countries, warrant officers also carry out the duties of NCOs. The naval equivalent includes some or all grades of petty officer, although not all navies class their petty officers as NCOs. There are different classes of non-commissioned officer, including junior non-commissioned officers (JNCO) and senior (or staff) non-commissioned officers (SNCO).
