Simple definition:
Money can be in the form of notes and coins or cheques, and can be kept in a bank.
Currency is the system or type of money that a country uses.
"money has a narrow definition called M1 and an alternative broad definition called M2. The narrow definition of M1 consists of currency—paper money and coins—in the hands of the nonbank public, plus checkable deposits in commercial banks and other depository institutions such as savings and loan associations."摘录自Branson H. William, Macroeconomic Theory and Policy. 是Princeton大学的中级宏观经济学教材,正好我刚看到这里,呵呵。