A department is an administrative sector of the government. It designates administrative areas of (a priori) centralized countries, e.g. the départements of France or the departamentos of Bolivia.
In some countries (e.g. United States, Switzerland), department is a term used instead of ministry to define a specific sector of the federal government, for example the Department of Justice or Department of Defense. Government departments are usually led by a secretary, administrator or director.
Department, is a term used, by the US Army, mostly prior to World War I. In 1920, most of the departments were redesignated as corps areas. However, the Hawaiian, Panama Canal, and Philippine Departments retained their old names. In 1939, the Puerto Rican Department was created and in May of 1941 the Panama Canal and Puerto Rican Departments were combined as the Caribbean Defense Command, although each was still referred to as a department.