A condition marked by extreme tiredness and inability to function due lack of energy. Fatigue may be acute or chronic.

A feeling of weariness, sleepiness or irritability after a period of mental or bodily activity. Seen in depression, anxiety, neurasthenia and somatoform disorders.

A lack of energy. A decrease over time in the ability to perform a physical or mental task.

A state of generalized weakness with a pronounced inability to summon sufficient energy to accomplish daily activities.

A subjective feeling of tiredness characterized by a lack of energy and motivation.

Everyone feels tired now and then. Sometimes you may just want to stay in bed. But, after a good night's sleep, most people feel refreshed and ready to face a new day. If you continue to feel tired for weeks, it's time to see your doctor. He or she may be able to help you find out what's causing your fatigue and recommend ways to relieve it. Fatigue itself is not a disease. Medical problems, treatments, and personal habits can add to fatigue. These include Taking certain medicines, such as antidepressants, antihistamines, and medicines for nausea and pain; Having medical treatments, like chemotherapy and radiation; Recovering from major surgery; Anxiety, stress, or depression; Staying up too late; Drinking too much alcohol or too many caffeinated drinks; Pregnancy. One disorder that causes extreme fatigue is chronic fatigue syndrome (CFS). This fatigue is not the kind of tired feeling that goes away after you rest. Instead, it lasts a long time and limits your ability to do ordinary daily activities. NIH: National Institute on Aging

Overall tiredness and lack of energy.

State of weariness following a period of exertion, mental or physical, characterized by a decreased capacity for work and reduced efficiency to respond to stimuli.

The state of weariness following a period of exertion, mental or physical, characterized by a decreased capacity for work and reduced efficiency to respond to stimuli.

Unusual tiredness and inability to perform usual activities.

(fatigue (lassitude)) A state of exhaustion usually caused by various etiologies such as a period of mental or bodily activity, sleep deprivation, medications, chronic disease, or other factors.

A disorder characterized by a state of generalized weakness with a pronounced inability to summon sufficient energy to accomplish daily activities.

Fatigue occurs most often as part of a symptom complex, but even when it is the sole or main presenting symptom, fatigue is one of the most common symptoms.

Fatigue, specific form of human inadequacy in which the individual experiences an aversion to exertion and feels unable to carry on. Such feelings may be generated by muscular effort; exhaustion of the energy supply to the muscles of the body, however, is not an invariable precursor. Feelings of...