Money refers to anything of value that is generally accepted as a medium of exchange. The demand for money is derived from its use in transactions and as a store of value. Legal tender laws require that a country's currency must be accepted for payment of debts. There are various definitions of money supply that include currency in circulation, demand deposits, savings accounts, and other assets that can be easily converted into cash. Inflation is a sustained increase in the general price level over time, and can be caused by factors that increase aggregate demand such as growth in the money supply, incomes, government spending, and capital inflows.