BobY, I love that title! What a wonderful thing to do to commodities!
In my experience, jam is in fact a bit different from preserves. Both contain pieces of fruit, but preserves, and marmalade for that matter, tend to be "looser". That is, they can pour off your spoon, albeit slowly. Jam just
sits there in a determined clump, even if you turn your spoon upside down. Mostly I see strawberry preserves on the grocery store shelves, yes, but occasionally strawberry jam as well. But I don't think I have ever heard of say,
blackberry or raspberry preserves. They are always jam or jelly, here.

Now--since you mention material (is that different than
"fabric", by the way, in the Harmony book?), I have seen, felt, and worn ramie cotton, and I am hoping you will tell me what the differences are between something labeled ramie and something labeled cotton.