A fatality; an event that leads to death.
"The fatal crash left three people dead on the highway."
In plain English: A fatal is not actually a noun; it is an adjective that means something deadly enough to cause death.
"The police released an official statement regarding the fatal in their report, though they did not specify which victim was involved until later that evening."
(of events) having extremely unfortunate or dire consequences; bringing ruin
"the stock market crashed on Black Friday"
"a calamitous defeat"
"the battle was a disastrous end to a disastrous campaign"
"such doctrines, if true, would be absolutely fatal to my theory"
"it is fatal to enter any war without the will to win it"
"a fateful error"
Proceeding from, or appointed by, fate or destiny.
"The fatal blow seemed destined to strike him exactly when his guard was down."
In plain English: Fatal means something that causes death immediately and cannot be stopped.
"The car crash was fatal because the driver did not survive the accident."
Usage: Use fatal only when something causes inevitable death, not merely as a synonym for serious or unfortunate events like "tragic." Avoid confusing it with accidental injuries where survival is possible, which should instead be described using terms like severe or life-threatening.
The word entered English directly from Middle French, which borrowed it unchanged from the Latin fātālis. In its original form, this term simply meant "related to fate."