the.com/critical
The word that means both life-or-death and that thing your aunt does at dinner.
means Either extremely important and decisive, or expressing disapproving judgment of someone or something.
from From Greek kritikos, able to discern or judge, born from krinein, to separate, decide, sift the good from the rubbish.
Nuclear senseA reactor goes critical when reactions self-sustain.
Medical senseCritical condition means the next hours decide everything.
Same rootCrisis, criterion, and critic are all siblings.