Fatal
Part of speech: adjective
Definition: Proceeding from, or appointed by, fate or destiny. Foreboding death or great disaster. Causing death or destruction.
Example sentence: Ideas are fatal to caste.
Mortal
Part of speech: adjective
Definition: Susceptible to death by aging, sickness, injury, or wound
Part of speech: noun
Definition: A human; someone susceptible to death.
Example sentence: Very few beings really seek knowledge in this world. Mortal or immortal, few really ASK. On the contrary, they try to wring from the unknown the answers they have already shaped in their own minds.