The trouble is, all of those words--tired, sleepy, fatigued--are just words. MSers use them and healthy people use them. I might use "tired" to mean I painted the barn and now I'm really tired. You might use "tired" to mean I was up most of the night and now I'm really tired.

Technically, fatigue is EXTREME tiredness, or mental/physical EXHAUSTION typically caused by stress or illness.

MSers (and some folks with other illnesses) go a step beyond that to extreme, crushing, dibilitating fatigue that isn't necessarily caused by anything other than having MS. It's fatigue on steroids.

To me, "tired" means more body or muscles, whereas not getting much sleep is "sleepy".

Even though it gives me the grrrrr's, I can't really blame people that don't get it, because you hear "fatigue" all the time referring to run-of-the-mill tiredness. So of COURSE when I say I'm dealing with fatigue, someone with three little kids and a full-time job is going to say "I know exactly what you mean!"

We need our own word that can't mean anything else than the kind of fatigue "we" get.