a medium of exchange的用法和样例：
- Money is a medium of exchange used to measure prices and debts.
- Robbins, again, would then be using butter as a medium of exchange.
- Currency Money in any form when in actual use as a medium of exchange, especially circulating paper money.
- The value of money is basically its value as a medium of exchange, or, as economists put it, its 'purchasing power.
- We look at the functions of money. Firstly it's a medium of exchange, so it's some commodity which facilitates the exchange of goods and services.