In common law, assault is the tort of acting intentionally, that is with either general or specific intent, causing the reasonable apprehension of an immediate harmful or offensive contact. Because assault requires intent, it is considered an intentional tort, as opposed to a tort of negligence. Actual ability to carry out the apprehended contact is not necessary.

As distinguished from battery, assault need not involve actual contact—it only needs intent and the resulting apprehension. However, assault requires more than words alone. For example, wielding a knife while shouting threats could be construed as assault if an apprehension was created. A battery can occur without a preceding assault, such as if a person is struck in the back of the head. Fear is not required, only anticipation of subsequent battery.

Three elements must be established in order to establish tortious assault: (1). the plaintiff apprehended immediate physical contact, (2). the plaintiff had reasonable apprehension (the requisite state of mind) and (3). the defendant's act of interference was intentional (the defendant intended the resulting apprehension). But intent for purposes of civil assault can be either general or specific. Specific intent means that when the defendant acted, he or she intended to cause apprehension of a harmful or unwanted contact. General intent means that the defendant knew with substantial certainty that the action would put someone in apprehension of a harmful or unwanted contact.

In law, assault is a crime which involves causing a victim to apprehend violence. The term is often confused with battery, which involves physical contact. The specific meaning of assault varies between countries, but can refer to an act that causes another to apprehend immediate and personal violence, or in the more limited sense of a threat of violence caused by an immediate show of force. Assault in some US jurisdictions^[which?] is defined more broadly still as any intentional physical contact with another person without their consent; but in the majority of the United States, and in England and Wales and all other common law jurisdictions in the world, this is defined instead as battery. Some jurisdictions have incorporated the definition of civil assault into the definition of the crime making it a criminal assault to intentionally cause another person to apprehend a harmful or offensive contact.

In common law, criminal assault often accompanied battery. See common assault. The elements of battery are (1) a volitional act (2) done for the purpose of causing a harmful or offensive contact with another person or under circumstances that make such contact substantially certain to occur and (3) which causes such contact. Thus throwing a rock at someone for the purpose of hitting him is a battery if the rock in fact strikes the person and is an assault if the rock misses. The fact that the person may have been unaware that the rock had been thrown at him is irrelevant under this definition of assault.

A tort, in common law jurisdictions, is a civil wrong. Tort law deals with situations where a person's behaviour has unfairly caused someone else to suffer loss or harm. A tort is not necessarily an illegal act but causes harm. The law allows anyone who is harmed to recover their loss. Tort law is different from criminal law, which deals with situations where a person's actions cause harm to society in general. A claim in tort may be brought by anyone who has suffered loss. Criminal cases tend to be brought by the state, although private prosecutions are possible.

Tort law is also differentiated from equity, in which a petitioner complains of a violation of some right. One who commits a tortious act is called a tortfeasor. The equivalent of tort in civil law jurisdictions is delict. Tort may be defined as a personal injury; or as "a civil action other than a breach of contract."

A person who suffers a tortious injury is entitled to receive "damages", usually monetary compensation, from the person or people responsible — or liable — for those injuries. Tort law defines what is a legal injury and, therefore, whether a person may be held liable for an injury they have caused. Legal injuries are not limited to physical injuries. They may also include emotional, economic, or reputational injuries as well as violations of privacy, property, or constitutional rights. Tort cases therefore comprise such varied topics as auto accidents, false imprisonment, defamation, product liability (for defective consumer products), copyright infringement, and environmental pollution (toxic torts), among many others.