Any act that is intended to cause pain, suffering, or damage to another person.

Aggressive behavior is often used to claim status, precedent, or access to an object or territory. While aggression is primarily thought of as physical, verbal attacks aimed at causing psychological harm also constitute aggression. In addition, fantasies involving hurting others can also be considered aggressive. The key component in aggression is that it is deliberate—accidental injuries are not forms of aggression.

Theories about the nature and causes of aggression vary widely in their emphases. Those with a biological orientation are based on the idea that aggression is an innate human instinct or drive. Sigmund Freud explained aggression in terms of a death wish...