Answer:
• as a medium of exchange, buyers can give it to sellers to pay for goods and services;
• as a unit of account, it can be used to add up apples and oranges in some common value;
• as a store of value, it can be used to transfer purchasing power into the future.
example:
A farmer who exchanges fruit for money can spend that money in the future; if he holds on to his fruit it might rot and no longer be useful for paying for something. INFLATION undermines the usefulness of money as a store of value, in particular, and also as a unit of account for comparing values at different points in time. HYPER-INFLATION may destroy confidence in a particular form of money even as a medium of exchange. Measures of LIQUIDITY describe how easily an ASSET can be exchanged for money (the easier this is, the more liquid is the asset).