The United States Army has three different rank categories: officers, warrant officers and enlisted members. Each of these classifications is further broken down into numerical rankings, with one being the lowest and nine being the highest in the enlisted and officer ranks and five being the highest warrant officer ranking.
The officer class outranks the other two classes. Warrant officers outrank enlisted members.
Officers generally enter the military with a four-year college degree and complete Officer Candidate School at Fort Benning, Georgia. The lowest officer rank is O-1, or second lieutenant. The O-2 through O-6 ranks are first lieutenant, captain, major, lieutenant general and colonel. O-7 to O-10 are the general ranks. In ascending order these are brigadier general, major general, lieutenant general and general. General of the Army is the highest possible officer rank, with the exception of a special Generals of the Army rank that has only been conferred twice as of 2015.
Army Warrant Officers are usually technical specialists who come from the higher enlisted ranks. Enlisted members with a rank of E-6 or higher can apply for Warrant Officer Candidate School. The numerical ranks for warrant officers are W01, CW2, CW3, CW4 and CW5.
Enlisted members are comprised of the ranks E-1 through E-9. The lowest rank is called "private," and Sergeant Major of the Army is the highest possible enlisted rank.