The total amount of money in an economy that is readily available for spending is called the money supply.
Its exact definition depends on the monetary aggregate being used. Narrow measures generally include physical currency and highly liquid bank deposits. Broader measures add less-liquid deposits and other near-money assets. Central banks and statistical agencies publish these measures using national definitions and classification systems.
Money supply is not identical to the amount of banknotes in circulation. Commercial banks create deposit money when they make loans, while repayments can reduce deposits. Central-bank actions, bank lending, public preferences, and financial regulation can therefore influence monetary aggregates.
Economists study money supply alongside prices, output, interest rates, and velocity. A larger money supply does not automatically produce proportional inflation, because its effects depend on how quickly money circulates and whether the economy has unused productive capacity.