The three functions/roles of money in an economy are:
1) Medium of Exchange: When money are used to intermediate exchange of goods and services.
2) Unit of Account: Standard numerical unit of measurement of market value goods, services, or other transaction. Money must be divisible into smaller units without loss of value and a specific weight or size to be verifiably countable.
3) Store of Value: To act as a store value,money should be reliably saved, stored, and retrieved. It also must be predictably usable as a medium of exchange when it is retrieved.