Fundamental volatility describes seemingly random price changes that do not revert. Any factor that determines fundamental values of a stock price can cause prices to change. The distinguishing characteristic of fundamental price changes is that they are caused by unexpected news about fundamental values and are unpredictable and permanent.
Uncertainty about fundamental factors often causes substantial fundamental volatility. The stocks of companies involved in technological research are often highly volatile, because their values are critically dependent on the outcomes of their research programs and the markets for products that presently do not exist.