critical (adj.) Look up critical at Dictionary.com
1580s, "censorious," from critic + -al (1). Meaning "pertaining to criticism" is from 1741; medical sense is from c.1600; meaning "of the nature of a crisis" is from 1640s; that of "crucial" is from 1841, from the "decisive" sense in Latin criticus. Related: Criticality (1756; in the nuclear sense, 1950); critically (1650s, "accurately;" 1815, "in a critical situation"). In nuclear science, critical mass is attested from 1940.