Beta
Beta measures how much a stock moves relative to the market as a whole. A beta of 1 means the stock tends to move in line with the index; above 1 it amplifies both rises and falls; below 1 it dampens them. It is the parameter that translates market risk in the CAPM, and it is computed from historical data, so it describes the past rather than promising the future.
See also
See it on real data
Celsmar computes this from the accounts companies file with their regulator, and shows which line every figure comes from. Free to start, no card.
Definition for informational purposes. It is not financial advice nor a recommendation to buy or sell.