perceive vs spy

perceive is not a noun while spy is a noun.

Word	Noun	Adjective	Verb	Adverb
perceive	No	No	Yes	No
spy	Yes	No	Yes	No

As verbs, spy is a hyponym of perceive; that is, spy is a word with a more specific, narrower meaning than perceive:

perceive (noun)	spy (noun)
	(military) a secret agent hired by a state to obtain information about its enemies or by a business to obtain industrial secrets from competitors
	a secret watcher; someone who secretly watches other people

perceive (verb)	spy (verb)
become conscious of	secretly collect sensitive or classified information; engage in espionage
to become aware of through the senses	watch, observe, or inquire secretly
	catch sight of
	catch sight of; to perceive with the eyes