With respect to buying on margin, it is the money put up in a margin account to partially finance the purchase of securities, where the remainder is financed by borrowing the from a broker against interest and commissions. The securities bought are used as collateral.

In the world of futures, margin refers to the money kept in a futures account to insure contract performance and to protect the integrity and well-functioning of futures markets. This money doesn’t represent borrowed amounts, and therefore no interest accrues thereon. Furthermore, it is required of both the buyer and seller of a futures contract. Margin can be in the form of cash, marketable securities like treasuries, letters of credit, and so on.