Chronic fatigue syndrome (CFS) is a disorder that causes extreme fatigue. 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.
The main symptom of CFS is severe fatigue that lasts for 6 months or more. You also have at least four of these other symptoms:
•Feeling unwell for more than 24 hours after physical activity
•Pain in multiple joints
•Tender lymph nodes