sample vs coupon

sample and coupon both are nouns.

Word	Noun	Adjective	Verb	Adverb
sample	Yes	No	Yes	No
coupon	Yes	No	No	No

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

sample (noun)	coupon (noun)
a small part of something intended as representative of the whole	a test sample of some substance
items selected at random from a population and used to test hypotheses about the population	a negotiable certificate that can be detached and redeemed as needed
all or part of a natural object that is collected and preserved as an example of its class

sample (verb)	coupon (verb)
take a sample of