currency vs monetary system

currency and monetary system both are nouns.

Word	Noun	Adjective	Verb	Adverb
currency	Yes	No	No	No
monetary system	Yes	No	No	No

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

currency: the metal or paper medium of exchange that is presently used
monetary system: anything that is generally accepted as a standard of value and a measure of wealth in a particular country or region

Other hypernyms of currency include medium of exchange.

currency (noun)	monetary system (noun)
the property of belonging to the present time	anything that is generally accepted as a standard of value and a measure of wealth in a particular country or region
general acceptance or use
the metal or paper medium of exchange that is presently used