canary vs stoolpigeon

canary and stoolpigeon both are nouns.

Word	Noun	Adjective	Verb	Adverb
canary	Yes	Yes	No	No
stoolpigeon	Yes	No	No	No

As nouns, canary and stoolpigeon are synonyms defined as:

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

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

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

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