greenback vs folding money

greenback and folding money both are nouns.

Word	Noun	Adjective	Verb	Adverb
greenback	Yes	No	No	No
folding money	Yes	No	No	No

As nouns, folding money is a hypernym of greenback; that is, folding money is a word with a broader meaning than greenback:

greenback: a piece of paper money (especially one issued by a central bank)
folding money: currency issued by a government or central bank and consisting of printed paper that can circulate as a substitute for specie

Other hypernyms of greenback include paper currency, paper money.

greenback (noun)	folding money (noun)
a piece of paper money (especially one issued by a central bank)	currency issued by a government or central bank and consisting of printed paper that can circulate as a substitute for specie