Margin

(1) Difference between the buying and selling rates, also used to indicate the discount or premium between spot or forward.
(2) A payment made by buyers and sellers of exchange traded futures and hedging contracts and writers of exchange traded options to demonstrate their ability to cover their potential losses on their position.
(3) In securities markets, the collateral deposited by a customer to secure a loan from a broker to purchase shares. In organisations with a CCP, the deposit of collateral to guarantee performance on an obligation or cover potential market movements on unsettled transactions is sometimes referred to as margin.
(4) The percentage reserve required by the US Federal Reserve to make an initial credit transaction.