crit·i·cal·i·ty 
(krĭt′ĭ-kălĭ-tē)
(krĭt′ĭ-kălĭ-tē)n. pl. crit·i·cal·i·ties
1. The quality, state, or degree of being of the highest importance: "The challenge of our future food supply is approaching criticality" (New York Times).
2. Physics
a. The point at which a nuclear reaction is self-sustaining.
b. The state of a substance or system at its critical point.