Liquidity describes the degree to which an asset or security can be quickly bought or sold in the market without affecting the asset's price.
Market liquidity refers to the extent to which a market, such as a country's stock market or a city's real estate market, allows assets to be bought and sold at stable prices.
There are several ways to define "money", but standard measures usually include currency in circulation and demand deposits (depositors' easily accessed assets on the books of financial institutions).
Money supply data are recorded and published, usually by the government or the central bank of the country.
This is one reason for the reliance on monetary policy as a means of controlling inflation.