rain vs deluge

rain and deluge both are nouns.

Word	Noun	Adjective	Verb	Adverb
rain	Yes	No	Yes	No
deluge	Yes	No	Yes	No

As nouns, deluge is a hyponym of rain; that is, deluge is a word with a more specific, narrower meaning than rain:

rain (noun)	deluge (noun)
anything happening rapidly or in quick successive	a heavy rain
water falling in drops from vapor condensed in the atmosphere	the rising of a body of water and its overflowing onto normally dry land
drops of fresh water that fall as precipitation from clouds	an overwhelming number or amount

rain (verb)	deluge (verb)
precipitate as rain	fill or cover completely, usually with water
	charge someone with too many tasks
	fill quickly beyond capacity; as with a liquid