shorten vs lessen

shorten and lessen both are verbs.

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

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

Other hypernyms of shorten include decrease, diminish, fall.

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

Other hypernyms of shorten include decrease, minify.

shorten (verb)	lessen (verb)
become short or shorter	decrease in size, extent, or range
make shorter than originally intended; reduce or retrench in length or duration	wear off or die down
reduce in scope while retaining essential elements	make become smaller
edit by omitting or modifying parts considered indelicate
make short or shorter