In engineering, survivability is the quantified ability of a system, subsystem, equipment, process, or procedure to continue to function during and after a natural or man-made disturbance; e.g. nuclear electromagnetic pulse from the detonation of a nuclear weapon.

For a given application, survivability must be qualified by specifying the range of conditions over which the entity will survive, the minimum acceptable level or post-disturbance functionality, and the maximum acceptable outage duration.

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Source: from Federal Standard 1037C in support of MIL-STD-188