The term Unified Command in the Incident Command System is:

The term Unified Command in the Incident Command System refers specifically to situations where multiple agencies or jurisdictions are involved in managing an incident. This concept is essential to ensure a coordinated response when different organizations, such as fire departments, police departments, and emergency medical services, must work together in addressing an incident.

Unified Command allows these agencies to collaborate without losing their individual identities or operational capabilities. Each agency maintains its own command structure while working towards common objectives, thus streamlining communication and decision-making during complex incidents. This arrangement enhances the overall effectiveness of the response and minimizes confusion that could arise from having multiple commands directing activities.

The other options, while they touch on aspects of emergency management, do not accurately reflect the specific defined nature of Unified Command. For example, the idea of starting small and expanding pertains more to the scaling of operations rather than command structure. Breaking down tasks is characteristic of task organization but does not specifically address the multi-agency aspect. Lastly, having a single direct supervisor is related to the chain of command principle, which differs from the collaborative approach of Unified Command in multi-agency scenarios.