Margin

Margin

 * Borrowed money that is used to purchase securities. This practice is referred to as "buying on margin".

Also, the amount of equity contributed by a customer as a percentage of the current market value of the securities held in a margin account.

- from Investopedia

Alternatively, "margin" is collateral that the holder of a position in securities, options, or futures contracts has to deposit to cover the credit risk of his counterparty (most often his broker). This risk can arise if the holder has done any of the following:


 * borrowed cash from the counterparty to buy securities or options,
 * sold securities or options short, or
 * entered into a futures contract.

The collateral can be in the form of cash or securities, and it is deposited in a margin account. On U.S. futures exchanges, "margin" was formally called performance bond.

- from Wikipedia

Margin Trading

 * Margin trading involves borrowing against securities you already own to purchase additional securities. By leveraging your assets, you can potentially realize greater investment returns.

- from Fidelity

Links

 * Margin, on Investopedia
 * How Margin Works, from Fidelity
 * Margin (finance), on Wikipedia
 * Definitions of margin on Google