A non-commissioned officer (NCO) is a military officer who has not earned a commission.[1][2][3] Non-commissioned officers usually obtain their position of authority by promotion through the enlisted ranks.[4] 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.[citation needed]