Stress (psychology), an unpleasant state of emotional and physiological arousal that people experience in situations that they perceive as dangerous or threatening to their well-being. The word stress means different things to different people. Some people define stress as events or situations that cause them to feel tension, pressure, or negative emotions such as anxiety and anger. Others view stress as the response to these situations. This response includes physiological changes-such as increased heart rate and muscle tension-as well as emotional and behavioral changes. However, most psychologists regard stress as a process involving a person's interpretation and response to a threatening event.

Stress is a common thing we all experience. We may feel stress when we are very busy, have important deadlines to meet, or have too little time to finish all of our tasks. Often people experience stress because of problems at work or in social relationships, such as a poor evaluation by a supervisor or an argument with a friend. Some people may be particularly vulnerable to stress in situations involving the threat of failure or personal humiliation. Others have extreme fears of objects or things associated with physical threats-such as snakes, illness, storms, or flying in an airplane-and become stressed when they encounter or think about these perceived threats. Major life events, such as the death of a loved one, can cause severe stress.

Stress can have both positive and negative effects. Stress is a normal, adaptive reaction to threat. It signals danger and prepares us to take defensive action. Fear of things that pose realistic threats motivates us to deal with them or avoid them. Stress also motivates us to achieve and fuels creativity. Although stress may hinder performance on difficult tasks, moderate stress seems to improve motivation and performance on less