What term describes the traditional roles and mission of each branch of service?

The term that best describes the traditional roles and mission of each branch of service is "functions." In a military context, "functions" refer to the specific responsibilities and operational capabilities assigned to each branch. These functions encompass the unique missions each service is designed to execute, such as the Air Force's focus on air and space operations, the Army's focus on land warfare, the Navy's emphasis on naval operations, and the Marine Corps' roles in amphibious assaults and expeditionary warfare.

While "roles" and "capabilities" might seem similar, they do not fully capture the comprehensive nature of what "functions" entails. "Roles" can describe general responsibilities or tasks assigned to a branch, but "functions" more accurately addresses the structured missions and operational tasks each service branch has cultivated over its history. "Capabilities," meanwhile, refer specifically to the abilities and assets available to perform those functions, rather than the broader mission context. "Tasks" often denote individual assignments within those broader functions and may not encompass the full range of responsibilities associated with a service branch's mission. Thus, "functions" encompasses the traditional and core missions that define how each branch serves within the armed forces.