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Uncertainty is

[the] degree to which a calculated, estimated, or observed value may deviate from the true value.[1]
[a] condition, event, outcome, or circumstance of which the extent, value, or consequence is not predictable.[2]
the state, even partial, of deficiency of information related to, understanding or knowledge of an event, its consequence, or likelihood.[3]
The inability to know in advance the exact likelihood or impact of future events.[4]
[t]he state of being not known, indeterminate, questionable, variable.[5]


Uncertainty may stem from many causes, including the lack of information. The concept of uncertainty is useful in understanding that likelihoods and consequences can oftentimes not be predicted with a high degree of precision or accuracy.[6]


  1. DHS Risk Lexicon, at 38.
  2. Glossary of Defense Acquisition Acronyms and Terms (July 2011) (full-text).
  3. ISO/IEC 31000:2009, at §2.1.
  4. Playbook: Enterprise Risk Management for the U.S. Federal Government, at 103.
  5. ICS-CERT, Common Cyber Security Language (full-text).
  6. DHS Risk Lexicon, at 38.