plural of femme fatale firefly

A very rare autosomal-dominant inherited prion disease of the brain, in which progressively worsening insomnia leads to hallucinations and delirium.

plural of case fatality rate

(pathology, epidemiology, statistics) A percentage derived by the division of the number of fatalities by the number of confirmed (diagnosed) cases (sufferers) of a disease.

(computing) An error that occurs when an operating system halts, because it has reached a condition where it can no longer operate safely.

plural of fatal system error