US currency may say “In God We Trust” but in order for the bills to mean anything, we place our trust in the US government. US currency is a type of fiat currency (as opposed to a commodity money) that has the backing of the US government. In order for something to be considered money, it must serve three general properties: store of value, a unit of account, and a medium of exchange. Each can be seen in the clip above. A lemonade seller won’t accept just anything, they want money (medium of exchange). We know the price of the lemonade because we use dollars as a measure of its worth (unit of account) and we expect those dollars to be worth the same amount over a certain period time (store of value).