The ability of an investment strategy to outperform the market, or its "edge," is referred to in the investing world as alpha. As a result, alpha is also frequently referred to as "excess return" or "abnormal rate of return," which relates to the notion that because markets are efficient, it is impossible to consistently generate returns that are higher than those of the general market. 

The Greek letter beta, which represents the total volatility or risk of the broad market (sometimes referred to as systematic market risk), is frequently employed in conjunction with alpha.