Violence is a general term to describe actions, usually deliberate, that cause or intend to cause injury to people, animals, or non-living objects. Violence is often associated with aggression. There are essentially two kinds of violence: random violence, which describes small-scale acts of random or targeted violence, and coordinated violence, which describes actions carried out by sanctioned or unsanctioned violent groups, such as war and terrorism.
Certain forms and degrees of violence are socially and/or legally sanctioned, while others constitute crimes within a specific society. Different societies apply different standards relating to sanctioned and non-sanctioned forms of violence. Degrees of violence that are not accepted by a society's norms are commonly regarded as cruel, and may be termed extra-normal violence. Violence used in terrorism is often extra-normal in terms of degree.
Violence can be unilateral, while fighting implies a reaction, at least a defensive one.
The psychologist James W. Prescott performed a study about the cause of violence in the anthropological sense.