What are the three roles of money in an economy

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.