Main Entry: crit·i·cal

Pronunciation: \ˈkrit-i-kəl\

Function: adjective

1 a : relating to, indicating, or being the stage of a disease at which an abrupt change for better or worse may be anticipated with reasonable certainty <the critical phase of a fever> b : being or relating to an illness or condition involving danger of death <critical care> <a critical head injury>
2 a : of sufficient size to sustain a chain reaction—used of a mass of fissionable material b : sustaining a chain reaction—used of a nuclear reactor

—crit·i·cal·ly \-k(ə-)lē\ adverb