mitigate vs lessen

mitigate and lessen both are verbs.

Word	Noun	Adjective	Verb	Adverb
mitigate	No	No	Yes	No
lessen	No	No	Yes	No

As verbs, lessen is a hypernym of mitigate; that is, lessen is a word with a broader meaning than mitigate:

Other hypernyms of mitigate include decrease, minify.

mitigate (verb)	lessen (verb)
to temper	decrease in size, extent, or range
lessen or to try to lessen the seriousness or extent of	wear off or die down
	make become smaller