sleet vs downfall

sleet and downfall both are nouns.

Word	Noun	Adjective	Verb	Adverb
sleet	Yes	No	Yes	No
downfall	Yes	No	No	No

As nouns, downfall is a hypernym of sleet; that is, downfall is a word with a broader meaning than sleet:

sleet: partially melted snow (or a mixture of rain and snow)
downfall: the falling to earth of any form of water (rain or snow or hail or sleet or mist)

Other hypernyms of sleet include precipitation.

sleet (noun)	downfall (noun)
partially melted snow (or a mixture of rain and snow)	a sudden decline in strength or number or importance
	failure that results in a loss of position or reputation
	the falling to earth of any form of water (rain or snow or hail or sleet or mist)

sleet (verb)	downfall (verb)
precipitate as a mixture of rain and snow