cash vs currency

cash and currency both are nouns.

Word	Noun	Adjective	Verb	Adverb
cash	Yes	No	Yes	No
currency	Yes	No	No	No

As nouns, currency is a hypernym of cash; that is, currency is a word with a broader meaning than cash:

cash (noun)	currency (noun)
money in the form of bills or coins	the property of belonging to the present time
prompt payment for goods or services in currency or by check	general acceptance or use
	the metal or paper medium of exchange that is presently used

cash (verb)	currency (verb)
exchange for cash