crit·i·cal 
(krĭtĭ-kəl)
(krĭtĭ-kəl)adj.
1. Judging severely and finding fault: a writer who is very critical of the government's foreign policy.
2.
a. Relating to or characterized by criticism; reflecting careful analysis and judgment: a critical appreciation of the filmmaker's work.
b. Of, relating to, or characteristic of critics: a play that received great critical acclaim.
c. Including scholarly commentary and interpretation: a critical edition of Poe's stories.
3.
a. Forming or having the nature of a turning point; crucial or decisive: a critical point in the campaign. See Synonyms at decisive.
b. Medicine Being or relating to a grave physical condition, especially of a patient.
c. Being in or verging on a state of crisis or emergency: a critical shortage of food.
4. Extremely important or essential: a critical element of the plan; a second income that is critical to the family's well-being. See Synonyms at indispensable.
5. Mathematics Of or relating to a point at which a curve has a horizontal tangent line, as at a maximum or minimum.
6. Chemistry & Physics Of or relating to the value of a measurement, such as temperature, at which an abrupt change in a quality, property, or state occurs: A critical temperature of water is 100°C, its boiling point at standard atmospheric pressure.
7. Physics Capable of sustaining a nuclear chain reaction: The reactor has gone critical.
criti·cal·ly adv.
criti·cal·ness n.