redbreast vs robin redbreast

redbreast and robin redbreast both are nouns.

Word	Noun	Adjective	Verb	Adverb
redbreast	Yes	No	No	No
robin redbreast	Yes	No	No	No

As nouns, redbreast and robin redbreast are synonyms defined as:

redbreast and robin redbreast: small Old World songbird with a reddish breast

Other synonyms of redbreast include Erithacus rubecola, Old World robin, robin.

redbreast (noun)	robin redbreast (noun)
small Old World songbird with a reddish breast	small Old World songbird with a reddish breast