darken vs cloud

darken is not a noun while cloud is a noun.

Word	Noun	Adjective	Verb	Adverb
darken	No	No	Yes	No
cloud	Yes	No	Yes	No

As verbs, cloud is a hyponym of darken; that is, cloud is a word with a more specific, narrower meaning than darken:

Other hyponyms of darken include embrown, murk, dun, blind, dim, dim, bedim, benight, shade, shade off, shadow, overcast.

darken (noun)	cloud (noun)
	a group of many things in the air or on the ground
	a visible mass of water or ice particles suspended at a considerable altitude
	any collection of particles (e.g., smoke or dust) or gases that is visible
	suspicion affecting your reputation
	out of touch with reality
	a cause of worry or gloom or trouble

darken (verb)	cloud (verb)
become dark or darker	colour with streaks or blotches of different shades
make dark or darker	make milky or dull
tarnish or stain	make less clear
	place under suspicion or cast doubt upon
	make gloomy or depressed
	billow up in the form of a cloud
	make less visible or unclear
	make overcast or cloudy