In economics, the monetary base, or the money base (often called narrow money in the UK) is a term relating to the volume of money in the economy, or money supply.
US Monetary Base ... Central bankers... they often don't know where they are, let alone where they are heading; their maps and compasses are unreliable and their steering is wonky.
M0 is referred to as the "wide monetary base" or "narrow money" and M4 is referred to as "broad money" or simply "the money supply". M0: Cash outside Bank of England + Banks ...