Two warthogs preparing to fight<unk>  is overt or covert, often harmful, social interaction with the intention of inflicting damage or other harm upon another individual; although it can be channeled into creative and practical outlets for some. It may occur either reactively or without provocation. In humans,<unk>  can be caused by various triggers, from frustration due to blocked goals to feeling disrespected. Human<unk>  can be classified into direct and indirect<unk> ; whilst the former is characterized by physical or verbal behavior intended to cause harm to someone, the latter is characterized by behavior intended to harm the social relations of an individual or group. In definitions commonly used in the social sciences and behavioral sciences,<unk>  is an action or response by an individual that delivers something unpleasant to another person. Some definitions include that the individual must intend to harm another person. In an interdisciplinary perspective,<unk>  is regarded as "an ensemble of mechanism formed during the course of evolution in order to assert oneself, relatives or friends against others, to gain or to defend resources (ultimate causes) by harmful damaging means ... These mechanisms are often motivated by emotions like fear, frustration, anger, feelings of stress, dominance or pleasure (proximate causes) ... Sometimes aggressive behavior serves as a stress relief or a subjective feeling of power." Predatory or defensive behavior between members of different species may not be considered<unk>  in the same sense.<unk>  can take a variety of forms, which may be expressed physically, or communicated verbally or non-verbally: including anti-predator<unk> , defensive<unk>  (fear-induced), predatory<unk> , dominance<unk> , inter-male<unk> , resident-intruder<unk> , maternal<unk> , species-specific<unk> , sex-related<unk> , territorial<unk> , isolation-induced<unk> , irritable<unk> , and brain-stimulation-induced<unk>  (hypothalamus). There are two subtypes of human<unk> : (1) controlled-instrumental subtype (purposeful or goal-oriented); and (2) reactive-impulsive subtype (often elicits uncontrollable actions that are inappropriate or undesirable).<unk>  differs from what is commonly called assertiveness, although the terms are often used interchangeably among laypeople (as in phrases such as "an aggressive salesperson").
Aggression
Disinhibition
Dissociation 
Seclusion
Impaction
Perseveration
Derealization
Perspiration