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EU Definitions


The likelihood of an occurrence, an outcome or a result, where this can be estimated probabilistically. [1]

European Project Definitions

CIPRNet project

The CIPRNet project [2] uses the following definition:

Likelihood is the chance of something happening.

RESIN project

The RESIN project [3] gives the following definition:

The chance of a specific outcome occurring, where this might be estimated probabilistically. [4]

Other International Definitions


Likelihood: A probabilistic estimate of the occurrence of a single event or of an outcome, for example, a climate parameter, observed trend, or projected change lying in a given range. Likelihood may be based on statistical or modeling analyses, elicitation of expert views, or other quantitative analyses. [5]

National Definitions


Likelihood: The chance of an event or incident happening, whether defined, measured or determined objectively or subjectively.

Vraisemblance: Possibilité qu’un événement ou un incident se produise, que celle-ci soit définie, mesurée ou déterminée de manière objective ou subjective. [6]


Vraisemblance: Estimation de la possibilité qu’un scénario de menace ou un risque, se produise. Elle représente sa force d’occurrence. [7]

Likelihood: Estimate of the possibility that a threat scenario or a risk will occur. It represents the estimated level of possibility. [8]

Kingdom of Saudi Arabia

Likelihood: A weighted factor based on an analysis of the probability that a given threat is capable of exploiting a given vulnerability. (NISTIR 7298r2 Glossary of Key Information Security Terms) [9]


(I risikoanalyser) brukes ofte sannsynlighet som mål på hvor trolig vi mener det er at en bestemt hendelse vil inntreffe, gitt vårt kunnskapsgrunnlag. [10]

(In risk analyses) likelihood is often used as an expression of how likely we think it is that a specific event will occur, given our knowledge base. [11]

United Kingdom (UK)

Likelihood is the chance of an event or outcome occurring, usually expressed as a probability. [12]

United States

Estimate of the potential of an incident or event’s occurrence. [13]

Likelihood: A weighted factor based on a subjective analysis of the probability that a given threat is capable of exploiting a given vulnerability. (from: NIST SP 800-161) [14]

Standard Definition


Likelihood is the quantitative estimation that an action, event or incident may occur. [15]

ISO 73:2009

Chance of something happening. [16]

Discussion Topic

See also



  1. European Climate Adaptation Platform (CLIMATE-ADAPT) Glossary
  4. Mach, K.J., S. Planton and C. von Stechow (eds.). Climate Change 2014: Synthesis Report. Contribution of Working Groups I, II and III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. Annex II: Glossary. [Core Writing Team, R.K. Pachauri and L.A. Meyer (eds.)]. IPCC, Geneva, Switzerland, pp. 117-130.
  5. IPCC, 2012: Glossary of terms. In: Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation [Field, C.B., V. Barros, T.F. Stocker, D. Qin, D.J. Dokken, K.L. Ebi, M.D. Mastrandrea, K.J. Mach, G.-K. Plattner, S.K. Allen, M. Tignor, and P.M. Midgley (eds.). A Special Report of Working Groups I and II of the Intergovernmental Panel on Climate Change (IPCC). Cambridge University Press, Cambridge, UK, and New York, NY, USA, pp. 555-564.]
  6. Vocabulaire de la gestion des urgencies/Emergency Management Emergency Management Vocabulary 281 (2012)
  7. Méthode de classification et mesures principales, ANSSI (2014)
  8. Classification Method and Key Measures, ANSSI (2014)
  9. Cyber Security Framework Saudi Arabian Monetary Authority Version 1.0 May 2017
  10. DSB, National Risikobild 2014
  11. DSB, National Risk Analysis 2014
  12. The National Adaptation Programme: Making the country resilient to a changing climate, UK Government (2013)
  13. DHS Risk Lexicon 2010 Edition, September 2010
  14. NIST Glossary
  15. ISA WG7; IEC 62443-2-1(2010-11)
  16. ISO Guide 73:2009 Risk management -- Vocabulary