Risk is potential of losing something of value. Values (such as physical health, social status, emotional well being or financial wealth) can be gained or lost when taking risk resulting from a given action, activity and/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/or probability of a risk, and may vary person to person. Any human endeavor carries some risk, but some are much riskier than others.
== Definitions ==
The Oxford English Dictionary cites the earliest use of the word in English (in the spelling of ''risque'' from its Arabic original "رزق" ) which mean working to gain income gain and profit (see Wikipedia Arabic meaning ) as of 1621, and the spelling as ''risk'' from 1655. It defines ''risk'' as:
(Exposure to) the possibility of loss, injury, or other adverse or unwelcome circumstance; a chance or situation involving such a possibility.〔Oxford English Dictionary〕
# Risk is an uncertain event or condition that, if it occurs, has an effect on at least one () objective. (This definition, using project terminology, is easily made universal by removing references to projects).〔A Guide to the Project Management Body of Knowledge (4th Edition) ANSI/PMI 99-001-2008〕
# The probability of something happening multiplied by the resulting cost or benefit if it does. (This concept is more properly known as the 'Expectation Value' or 'Risk Factor' and is used to compare levels of risk)
# 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 (such as burning down of a building) is known but when a mode of occurrence or the actual value of the occurrence (whether the fire will occur at a particular property) is not.''(Reference needed)'' A risk is not an uncertainty (where neither the probability nor the mode of occurrence is known), a peril (cause of loss), or a hazard (something that makes the occurrence of a peril more likely or more severe).
# Securities trading: The probability of a loss or drop in value. Trading risk is divided into two general categories: (1) Systematic risk affects all securities in the same class and is linked to the overall capital-market system and therefore cannot be eliminated by diversification. Also called market risk. (2) Non-systematic risk is any risk that isn't market-related. Also called non-market risk, extra-market risk or diversifiable risk.
# Workplace: Product of the consequence and probability of a hazardous event or phenomenon. For example, the risk of developing cancer is estimated as the incremental probability of developing cancer over a lifetime as a result of exposure to potential carcinogens (cancer-causing substances).
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』