Department
A department was a major division or subdivision within the structure of an organization. 

According to Luther Sloan, Section 31 was "an autonomous department", a branch of Starfleet Intelligence that operated with the intent of protecting the Federation's best interests, meaning that they "don't submit reports or ask for approval for specific operations." ()

Specific departments

Earth
 Internal Affairs
 Detroit Department of Health
 Police department
 Detroit Police Department
 Los Angeles Police Department
 New York City Police Department
 Portage Creek Police Department
 San Francisco Police Department
 San Francisco Department of Sanitation

United Federation of Planets
 Bureau of Planetary Treaties
 Department of Cartography
 Department of Investigation
 Department of Foreign Studies
 Department of Temporal Investigations
 Macalintal Physics Department
 Temporal Mechanics Department
 Section 31