Among the many confusing things you have to deal with when trying to learn about fibromyalgia syndrome (FMS) and chronic fatigue syndrome (CFS or ME/CFS) is the difference between a disease and a syndrome.
When doctors who don’t believe in FMS or ME/CFS are quoted in articles, they frequently lean heavily on the distinction. The word “syndrome” itself has been so misused in the popular media that it sounds a bit silly and overblown. But really, what’s the difference?
http://chronicfatigue.about.com