Medium of exchange is a bit different. Successful currencies generally need some price stability, otherwise they are avoided or hoarded, and their use as a med

Medium of exchange is a bit different. Successful currencies generally need some price stability, otherwise they are avoided or hoarded, and their use as a medium of exchange vanishes. Historically this would happen with coins minted from precious metals like gold: when the price of gold rose above the face value of the coins, the coins disappeared from circulation.