Market liquidity

Liquidity describes how easily an item can be traded for another item, or into the common currency within an economy. Money is the most liquid asset because it is universally recognised and accepted as the common currency. In this way, money gives consumers the freedom to trade goods and services easily without having to barter.
Liquid financial instruments are easily tradable and have low transaction costs. There should be no — or minimal — spread between the prices to buy and sell the instrument being used as money.