β (Beta) is the second letter of the Greek alphabet, often used in various fields such as mathematics, science, and finance. In finance, it represents the measure of a stock's volatility in relation to the overall market. A β value greater than 1 indicates higher volatility, while a value less than 1 suggests lower volatility compared to the market. In mathematics, β can denote a specific type of function or variable in equations. Additionally, in statistics, it often represents the probability of making a Type II error in hypothesis testing. Its versatility makes β a significant symbol across multiple disciplines.