Non-commissioned officer

A non-commissioned officer (sometimes spelled noncommissioned officer and shortened to NCO or non-com (US)), called a sub-officer in some countries, is a military officer who has not been given a commission. Non-commissioned officers, in the English-speaking world, usually obtain their position of authority by promotion through the enlisted ranks.
NCOs usually include all grades of corporal and sergeant; in some countries, warrant officers also do the same things as NCOs. In the navy and depending on the country, some or all grades of petty officer may be counted as NCO's. There are different classes of non-commissioned officer, including junior non-commissioned officers (JNCO) and senior (or staff) non-commissioned officers (SNCO).