Stress can be defined as a force exerted when one body or body part presses on, pulls on, pushes against, or tends to compress or twist another body or body part. For example, geostress is the causal factor in all major landforms on the earth. The intensity of this mutual force is expressed in pounds per square inch. Stress can also refer to the deformation caused in a body by such a force.

Stress, in psychology and biology, is any strain or interference that disturbs the functioning of an organism. The human being responds to physical and psychological stress with a combination of psychic and physiological defenses. If the stress is too powerful, or the defenses inadequate, a psychosomatic disease, ailment or other mental disorder may result.

Stress is an unavoidable effect of living and is an especially complex phenomenon in modern technological society. There is little doubt that an individual's success or failure in controlling potentially stressful situations can have a profound effect on his ability to function. The ability to "cope" with stress has figured prominently in psychosomatic research. Researchers have reported a statistical link between coronary heart disease and individuals exhibiting stressful behavioral patterns designated "Type A." These patterns are reflected in a lifestyle characterized by impatience and a sense of time urgency, hard-driving competitiveness, and preoccupation with vocational and related deadlines.

Various strategies have been successful in treating psychological and physiological stress. Moderate stress may be relieved by exercise and any type of meditation (e.g., yoga or other Asian meditative forms). Severe stress may require psychotherapy to uncover and work through the underlying causes. A form of behavior therapy known as biofeedback enables the patient to become more aware of internal processes and thereby gain some control over bodily reactions to stress. Sometimes, a change of environment or living situation may produce therapeutic results.