"Definitions for Uncertainty, Risk, and their Measurements
Uncertainty: The lack of complete certainty, that is, the existence of more than one possibility. The “true” outcome/state/result/value is not known.
Measurement of Uncertainty: A set of probabilities assigned to a set of possibilities. For example: “There is a 60% chance this market will more than double in fi ve years, a 30% chance it will grow at a slower rate, and a 10% chance the market will shrink in the same period.”
Risk: A state of uncertainty where some of the possibilities involve a loss, catastrophe, or other undesirable outcome.
Measurement of Risk: A set of possibilities each with quantifi ed probabilities and quantifi ed losses. For example: “We believe there is a 40% chance the proposed oil well will be dry with a loss of $12 million in exploratory drilling costs.”
Trecho retirado de "How to Measure Anything - Finding the Value of “Intangibles” in Business" de Douglas Hubbard.