M0

A measure of the money supply which combines any liquid or cash assets held within a central bank and the amount of physical currency circulating in the economy. In the United Kingdom, the M0 supply is also referred to as narrow money.

M0 (M-zero) is the most liquid measure of the money supply. It only includes cash or assets that could quickly be converted into currency. This measure is known as narrow money because it is the smallest measure of the money supply.