twenty dollar bill vs bank note

twenty dollar bill and bank note both are nouns.

Word	Noun	Adjective	Verb	Adverb
twenty dollar bill	Yes	No	No	No
bank note	Yes	No	No	No

As nouns, bank note is a hypernym of twenty dollar bill; that is, bank note is a word with a broader meaning than twenty dollar bill:

Other hypernyms of twenty dollar bill include bank bill, banker's bill, banknote, bill, Federal Reserve note, government note, greenback, note.

twenty dollar bill (noun)	bank note (noun)
a United States bill worth 20 dollars	a piece of paper money (especially one issued by a central bank)