government note vs greenback

government note and greenback both are nouns.

Word	Noun	Adjective	Verb	Adverb
government note	Yes	No	No	No
greenback	Yes	No	No	No

As nouns, government note and greenback are synonyms defined as:

government note and greenback: a piece of paper money (especially one issued by a central bank)

Other synonyms of government note include bank bill, bank note, banker's bill, banknote, bill, Federal Reserve note, note.

government note (noun)	greenback (noun)
a piece of paper money (especially one issued by a central bank)	a piece of paper money (especially one issued by a central bank)