instance vs excuse

instance and excuse both are nouns.

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

As nouns, excuse is a hyponym of instance; that is, excuse is a word with a more specific, narrower meaning than instance:

Other hyponyms of instance include apology, exception, case in point, precedent, quintessence, sample, specimen.

instance (noun)	excuse (noun)
an item of information that is typical of a class or group	a poor example
an occurrence of something	a defense of some offensive behavior or some failure to keep a promise etc.
	a note explaining an absence

instance (verb)	excuse (verb)
clarify by giving an example 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