A precipitous decline in fortune; death or rapid deterioration, as in status or wealth.
Many economic and political reasons led to the downfall of the Roman Empire.
The cause of such a fall; a critical blow or error.
Orson Scott Card
It is the downfall of evil, that it never sees far enough ahead.
An act of falling down.
a downfall of rain
verb
(intransitive) To fall down; deteriorate; decline.
It should be noted that the magnitude of satellites decreases when tuning out of degeneracy, and in the wavelength range of 1.2-1.3 pm it downfalls to the value of 10-15% of the main spike magnitude.