decoy vs stool pigeon

decoy and stool pigeon both are nouns.

Word	Noun	Adjective	Verb	Adverb
decoy	Yes	No	Yes	No
stool pigeon	Yes	No	No	No

As nouns, stool pigeon is a hyponym of decoy; that is, stool pigeon is a word with a more specific, narrower meaning than decoy:

decoy: something used to lure fish or other animals into danger so they can be trapped or killed
stool pigeon: a dummy pigeon used to decoy others

Other hyponyms of decoy include chum, fish lure, fisherman's lure, ground bait.

decoy (noun)	stool pigeon (noun)
something used to lure fish or other animals into danger so they can be trapped or killed	a dummy pigeon used to decoy others
a beguiler who leads someone into danger (usually as part of a plot)	someone acting as an informer or decoy for the police

decoy (verb)	stool pigeon (verb)
lure or entrap with or as if with a decoy