What is Chronic Fatigue?
There are several case definitions for CFS and all require fatigue as one of the symptoms.

1.The individual has had severe chronic fatigue for 6 or more consecutive months and the fatigue is not due to ongoing exertion or other medical conditions associated with fatigue (these other conditions need to be ruled out by a doctor after diagnostic tests have been conducted)
2.The fatigue significantly interferes with daily activities and work
3.The individual concurrently has 4 or more of the following 8 symptoms:

A) post-exertion malaise lasting more than 24 hours
unrefreshing sleep
B) significant impairment of short-term memory or concentration
C) muscle pain
D) pain in the joints without swelling or redness
E) headaches of a new type, pattern, or severity
F) tender lymph nodes in the neck or armpit
G) a sore throat that is frequent or recurring

These symptoms should have persisted or recurred during 6 or more consecutive months of illness, and they cannot have first appeared before the fatigue.

The primary symptom of CFS is unexplained, severe fatigue lasting at least 6 months that is not improved by bed rest and that can get worse after physical activity or mental exertion. Individuals with CFS experience a fatigue so strong that their activity levels and stamina decline dramatically. However, fatigue is not the only symptom, and for some patients may not be the symptom that bothers them the most.