The definition is ... from Elroy Dimson at the London Business School: Risk means more things can happen than will happen.

That means you don't know the limits of what can happen, but you still have to make decisions. So you manage risks by comparing them to potential returns, and through diversification.

Source: Bernstein, Peter, (2007), Philosopher of Risk, Business Week, Apr 9, 2007

""Risk is just a very expensive substitute for information."" -- Slywotzky, The Upside.