canary vs stool pigeon

canary and stool pigeon both are nouns.

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

As nouns, canary and stool pigeon are synonyms defined as:

canary and stool pigeon: someone acting as an informer or decoy for the police

Other synonyms of canary include fink, sneak, sneaker, snitch, snitcher, stoolie, stoolpigeon.

canary (noun)	stool pigeon (noun)
any of several small Old World finches	a dummy pigeon used to decoy others
a moderate yellow with a greenish tinge	someone acting as an informer or decoy for the police
a female singer
someone acting as an informer or decoy for the police

canary (adjective)	stool pigeon (adjective)
having the color of a canary; of a light to moderate yellow