Psychologists define aggression as a range of behaviors that are intended to cause harm to others. While those behaviors often stem from anger, they can take root at a range of emotions such as jealousy, fear, or sadness, to name a few. Because the terms “aggression” and “violence” are used interchangeably in daily language, it is important to distinguish aggression from violence. Both aggression and violence can be physical, mental, or verbal. Violence, however, is an extreme expression of anger. Violence is defined as the enactment of aggression; it is an assault with intent to harm or injure others. Not all aggression leads to violence.

There are two broad categories of aggression; hostile aggression and instrumental aggression. Hostile aggression is accompanied by strong emotions, particularly anger, and is associated with impulsive, unplanned, or uncontrolled behavior. Instrumental aggression, in contrast, is a means to an end. It is often referred to as predatory aggression and is associated with goal-oriented, planned, hidden, or controlled behavior. In instrumental aggression, harming the person is used to obtain some other goal, such as money.