5 USC 2101 - Civil service; armed forces; uniformed services

For the purpose of this title
(1) the civil service consists of all appointive positions in the executive, judicial, and legislative branches of the Government of the United States, except positions in the uniformed services;
(2) armed forces means the Army, Navy, Air Force, Marine Corps, and Coast Guard; and
(3) uniformed services means the armed forces, the commissioned corps of the Public Health Service, and the commissioned corps of the National Oceanic and Atmospheric Administration.