A measure of a security’s price fluctuations (volatility) relative to an appropriate market index. For example, the Standard & Poor’s 500 Stock Index (S&P 500) has a beta of 1. Stocks with betas greater than 1 are subject to more rapid and extreme price fluctuations than the market. Conversely, price fluctuations for stocks with betas less than 1 are less frequent and smaller than the market. Conservative investors generally seek lower beta securities, while aggressive investors seek higher betas.