The common law of the United States allows for a variety of torts that can be committed. Assault is the tort of intentionally and voluntarily causing a reasonable apprehension of an immediate or offensive contact. Assault, like battery, is a trespass to person. It is designed to protect a person’s interest in living without apprehension of harm. Assault requires intent, making it an intentional tort, as opposed to a tort of negligence.
Assault only requires that a person have apprehension of impending harm, so it does not matter if the person committing the assault can actually carry through with the threat. This means that if a person is held up with a toy gun, it does not matter that the toy gun will not be able to harm a person. It only matters that the victim felt apprehension.
Assault is distinguishable from battery in that it does not require actual contact. It only needs intent and apprehension. A person wielding a knife, even if no contact between the knife and a person is made, can be said to have assaulted a person. Like battery, intent can be transferred from one person to another. This means that if a person is behind a person who is being threatened, he or she can claim to have been assaulted if they felt apprehension.
The law varies by jurisdiction, of course, but contact is frequently defined as “harmful” if it objectively could injure, disfigure, impair, or cause pain to another person. An act is “offensive” if it would offend a reasonable person’s sense of personal dignity.