Deterrence is the idea or theory that the threat of punishment will deter people from committing crime and reduce the probability and/or level of offending in society). It is one of five objectives that punishment is thought to achieve; the other four objectives are denunciation, incapacitation (for the protection of society), retribution, and rehabilitation). Deterrence can be applied in two ways: punishments imposed on individual offenders will deter or prevent that particular offender from committing further crimes, and public knowledge that certain offenses will be punished has a general deterrent effect that prevents others from committing crimes).

There are two different aspects of punishment that may have an impact on deterrence. The first is the certainty of punishment, which increases the likelihood of apprehension and punishment, and this may have a deterrent effect. The second relates to the severity of punishment; how severe the punishment is for a particular crime may influence behavior if the potential offender concludes that the punishment is so severe, it is not worth the risk of getting caught).

Deterrence is not only applicable to criminal justice but also to foreign policy. In foreign policy, deterrence means dissuading bad behavior with the threat of significant punishment. The threat of punishment can be used to prevent countries from engaging in aggressive behavior towards other countries.

In summary, deterrence is the act of preventing bad behavior by threatening punishment. It can be applied in criminal justice and foreign policy. The certainty of punishment and the severity of punishment are two aspects of deterrence that can influence behavior.