Risk is potential of losing something of value. Values can be gained or lost when taking risk resulting from a given action or inaction, foreseen or unforeseen. Risk can also be defined as the intentional interaction with uncertainty. Uncertainty is a potential, unpredictable, unmeasurable and uncontrollable outcome; risk is a consequence of action taken in spite of uncertainty.
Risk perception is the subjective judgment people make about the severity and probability of a risk, and may vary person to person. Any human endeavor carries some risk, but some are much riskier than others.
Risk is an uncertain event or condition that, if it occurs, has an effect on at least one objective. .
The probability of something happening multiplied by the resulting cost or benefit if it does.
The probability or threat of quantifiable damage, injury, liability, loss, or any other negative occurrence that is caused by external or internal vulnerabilities, and that may be avoided through preemptive action.
Finance: The possibility that an actual return on an investment will be lower than the expected return.
Insurance: A situation where the probability of a variable is known but when a mode of occurrence or the actual value of the occurrence is not. A risk is not an uncertainty , a peril , or a hazard . (source : wikipedia)