An officer is a person who holds a position of authority as a member of an armed force or uniformed service.
Broadly speaking, "officer" means a commissioned officer, a non-commissioned officer (NCO), or a warrant officer. However, absent contextual qualification, the term typically refers only to a force's commissioned officers, the more senior members who derive their authority from a commission from the head of state.
The United States Public Health Service Commissioned Corps (USPHSCC; also referred to as the Commissioned Corps of the United States Public Health Service) is the uniformed service branch of the United States Public Health Service and one of the eight uniformed services of the United States (along with the Army, Navy, Marine Corps, Coast Guard, Air Force, Space Force, and NOAA Commissioned Officer Corps). The commissioned corps' primary mission is the protection, promotion, and advancement of health and safety of the general public.
Along with the NOAA Commissioned Officer Corps, the Public Health Service Commissioned Corps is one of two uniformed services that consist only of commissioned officers and has no enlisted or warrant officer ranks, although warrant officers have been authorized for use within the service. Officers of the commissioned corps are classified as noncombatants, unless directed to serve as part of the military by the president or detailed to a service branch of the military. Members of the commissioned corps wear uniforms modeled after the United States Navy and the United States Coast Guard, with special Public Health Service Commissioned Corps insignia, and hold naval ranks equivalent to officers of the Navy and Coast Guard, along with corresponding in-service medical titles. Commissioned corps officers typically receive their commissions through the commissioned corps's direct commissioning program.
A cadet is a student or trainee within various organisations, primarily in military contexts where individuals undergo training to become commissioned officers. However, several civilian organisations, including civil aviation groups, maritime organisations, and police services, also designate their auxiliary members and trainees as cadets.
A rear admiral is one of two distinct ranks of commissioned officers in four of the uniformed services of the United States; "rear admiral (lower half)", a one-star flag officer, and "rear admiral", a two-star flag officer. The two ranks are only utilized by the United States Navy, U.S. Coast Guard, U.S. Public Health Service Commissioned Corps, and the National Oceanographic and Atmospheric Administration Commissioned Officer Corps. In contrast, in most other nations' rank-bearing services the term "rear admiral" refers exclusively to two-star flag officer rank.