MONEY in circulation among the public at a particular point of time is called money supply. Its types are:Narrow MoneyBroad MoneyPhysical money such as currency and coins KNOWN as Narrow money.M1 & M2 can be easily converted to CASH, hence called as Narrow Money.M3 & M4 can't be easily converted to cash, hence called as Broad Money. M1 = Currency (C) + Demand Deposits (DD) +Other deposits with RBIM2 = M1 + Post Office (Savings)M3 = M1 + Time Deposits (TD)M4 = M3 + Post Office (Total)M1 is the most liquid and easiest for transactions whereas, M4 is the least liquid of all.Note 1: M1 Exclude INDIA's deposits with IMF, World Bank, Foreign Government etc. and interbank depositsNote 2: The interbank Deposits, which a commercial bank holds in other commercial banks, are not to be regarded as PART of the money supply.