评估一种证券系统性风险的工具，用以量度证券或投资证券组合相对总体市场的波动性。贝塔系数利用回归的方法计算：贝塔系数为1，即证券的价格与市场同幅度地变动；贝塔系数高于1，即证券价格的波动性比市场高；贝塔系数低于1，即证券价格的波动性比市场低。

A measure of the volatility, or systematic risk, of a security or a portfolio in comparison to the market as a whole. Beta is used in the capital asset pricing model (CAPM), a model that calculates the expected return of an asset based on its beta and expected market returns..

Also known as "beta coefficient".

Beta is calculated using regression analysis, and you can think of beta as the tendency of a security's returns to respond to swings in the market. A beta of 1 indicates that the security's price will move with the market. A beta of less than 1 means that the security will be less volatile than the market. A beta of greater than 1 indicates that the security's price will be more volatile than the market. For example, if a stock's beta is 1.2, it's theoretically 20% more volatile than the market.

Many utilities stocks have a beta of less than 1. Conversely, most high-tech Nasdaq-based stocks have a beta of greater than 1, offering the possibility of a higher rate of return, but also posing more risk.