essential functions The term national essential functions means that subset of Government functions that are necessary to lead and sustain the Nation during a catastrophic emergency. (6) Primary mission essential functions The term primary mission essential functions means those Government functions that must be performed in order to support or implement the performance of the national essential functions before, during, and in the aftermath of an emergency. (7) Resilience The term resilience means the ability to prepare for and adapt to changing conditions and withstand and recover rapidly from disruptions. The term includes the ability to withstand and recover from deliberate attacks, accidents, or naturally occurring threats or incidents. (8) Sector-specific agency