Agreements to buy or sell a standardized value of a stock index, on a future date at a specified price, such as trading New York Stock Exchange composite index on the New York Futures Exchange (NYFE). As an investment instrument it combines features of securities trading based on stock indices with the features of commodity futures trading. It allows investors to speculate on the entire stockmarket's performance, short sell (see short sale) an index with a futures contract, or to hedge a long position against a decline in value.