instance vs specimen

instance and specimen both are nouns.

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

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

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

instance (noun)	specimen (noun)
an item of information that is typical of a class or group	a bit of tissue or blood or urine that is taken for diagnostic purposes
an occurrence of something	an example regarded as typical of its class

instance (verb)	specimen (verb)
clarify by giving an example of