Beta, β or the beta coefficient is one of “The Greeks”. It describes how much the movement of the market as a whole affects the movement of a given stock. For instance, a stock with a beta of 0.75 moves up or down 75 points for every 100 points that the market as a whole moves. A beta that is greater than one indicates a volatile stock. In some cases, beta can be negative (i.e. the price of the security increases when the rest of the market falls, or vice versa), but this is extremely rare.