relax vs lessen

relax and lessen both are verbs.

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

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

Other hypernyms of relax include decrease, minify.

relax (verb)	lessen (verb)
become less tense, rest, or take one's ease	decrease in size, extent, or range
cause to feel relaxed	wear off or die down
make less taut	make become smaller
become loose or looser or less tight
make less active or fast
become less severe or strict
make less severe or strict
become less tense, less formal, or less restrained, and assume a friendlier manner