silver certificate vs bank bill

silver certificate and bank bill both are nouns.

Word	Noun	Adjective	Verb	Adverb
silver certificate	Yes	No	No	No
bank bill	Yes	No	No	No

As nouns, bank bill is a hypernym of silver certificate; that is, bank bill is a word with a broader meaning than silver certificate:

silver certificate: formerly a bank note issued by the United States Treasury and redeemable in silver
bank bill: a piece of paper money (especially one issued by a central bank)

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

silver certificate (noun)	bank bill (noun)
formerly a bank note issued by the United States Treasury and redeemable in silver	a piece of paper money (especially one issued by a central bank)