@WBYeats,
Quote:According to JTT, AN XYZ TONE and XYZ TONES are the same in meaning;
They are equal in meaning when they are equal, WB, and they are not equal when they are not equal.
Quote:I usually say 'solid fuel', but 'nuclear fuels'; can I on that analogy say FUEL and FUELS are interchangeble in meaning?
Yes, you can say that when they are but you can't say that when they aren't.
Now if I sounded a bit snotty or a lot snotty above, rest assured that I wasn't trying to be.
As I have said many times, CONTEXT is SO important. And this context can be VERY SMALL NUANCES.
Read those last few sentences as they are vitally important. I know that you want to hear some big general rule/guideline that will help you but I'll say with some measure of assurance that there isn't one in these cases you've brought up.
I'm not trying to stop you, or even discourage you from asking more questions. But instead of asking a big GENERAL question, why not try developing some examples where you use 'nuclear fuels' or 'nuclear fuel'.
That may well give us a much better opportunity to help you.
I have a good example of what I've been talking about above, from the CGEL but I don't want to type it out now. Remind me to do so if I forget.