Related to Mutual Funds: Measures a Fund's relative volatility, as compared to a standard market index, such as the S&P 500. (By definition a market's beta will always be equal to one.) A Fund with a higher beta (more than 1) is more volatile than the market.

Related to Equities: Beta is used to measure the volatility of a stock's price relative to the general market. The S&P 500 index is used as a proxy for the general market. Betas are shown for all U.S. stocks where a five-year trading history is available. A stock with a higher beta (more than 1) is more volatile than the market and vice versa.