A deterrent is something that discourages or prevents a person from taking a certain action. It can be a consequence or a fear that makes someone think twice before engaging in behavior that is considered undesirable or harmful. For example, the presence of police officers can act as a deterrent to crime, as individuals may be less likely to commit illegal acts when they know there is a chance of getting caught. Deterrents can be used in various contexts, including law enforcement, military strategy, and even personal decision-making. In the context of nuclear weapons, the idea of mutually assured destruction serves as a deterrent against nuclear war, as countries are less likely to attack if they know it could lead to their own destruction.