When someone asks what's going on with me, I don't tell them I have chronic fatigue. I tell them how it feels and what the symptoms are. If they press on, I tell them what tests I've had and that doctors find no clear answer. If the person continues to ask questions, and seem very concerned, I will explain that some doctors have suggested chronic fatigue, that chronic fatigue is a syndrome, and that a syndrome is a collection of symptoms for which there is no clear explanation or treatment. I also tell them that I'm still trying to find answers. Of course, I don't do it as tersely as I did it above. But I've only gotten one snide remark in the year I've been doing it this way.