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.