One of two broad categories of Exchange-Traded Funds, based on four widely used indices: Spdrs, based on Standard & Poor's 500 Composite Stock Price Index; MidCap SPDRs, based on the S&P MidCap 400 Index; the Nasdaq-100 Index Tracking Stock SM; and Diamonds, based on the Dow Jones Industrial Averages. See also Exchange-Traded Funds; Index Shares.




