define uncertainty
Definition of uncertainty. 1  1 : the quality or state of being uncertain : doubt. 2  2 : something that is uncertain.
Situations often arise wherein a decision must be made when the results of each possible choice are uncertain. Uncertainty is a situation which involves imperfect and/or unknown information. However, uncertainty is an unintelligible expression without a straightforward description. It arises in subtly different ways in a number of fields, including insurance, philosophy, physics, statistics, economics, finance, psychology, sociology, engineering, metrology, and information science.