extenuate vs excuse

extenuate is not a noun while excuse is a noun.

Word	Noun	Adjective	Verb	Adverb
extenuate	No	No	Yes	No
excuse	Yes	No	Yes	No

As verbs, excuse is a hypernym of extenuate; that is, excuse is a word with a broader meaning than extenuate:

Other hypernyms of extenuate include apologise, apologize, rationalise, rationalize.

extenuate (noun)	excuse (noun)
	a poor example
	a defense of some offensive behavior or some failure to keep a promise etc.
	a note explaining an absence

extenuate (verb)	excuse (verb)
lessen or to try to lessen the seriousness or extent of	accept an excuse for
	defend, explain, clear away, or make excuses for by reasoning
	excuse, overlook, or make allowances for; be lenient with
	serve as a reason or cause or justification of
	grant exemption or release to
	ask for permission to be released from an engagement