Is it just the thinness and more exquisite turns of porcelain that make it different from pottery and stoneware....or is there some intrinsic difference between the two?

Is there some kind of clay that is never used in pottery, for instance, that is always used in porcelain?

Pottery feels heavier. Is it just because it is thicker?

And the glaze feels generally smoother on porcelain, but not necessarily so. I have some very smooth-feeling coffee mugs that aren't porcelain...but I honestly cannot say why they aren't other than they're simply heavier than our porcelain teacups.

of troy, you usually know about these types of questions. If you're around, could you (or anyone else) explain the basic differences between pottery and porcelain.

Thanks.

And: Is there a gray area where one is difficult to distinguish from the other (porcelain from pottery)?