Can any one explain the difference between 8 ply and 3 fold 8ply?
8 ply usually refers to the number of continuous fibers/strands. Then 3 of those clusters (of 8 strands each) are twisted, wrapped, or whatever other methods the spinner uses to make the final yarn.
Most yarns do have folds & plies, but not all of them list that on the label now. Now, most simply list the ply count. But when humans were the sole manufacturer, before the industrial age, their product was done in separate stages, wheras machines can sometimes merge or eliminate steps for various reasons.
Hope that helps!
To confuse the issue, Hobbii and Scheepjes (and probably others) make 8-strand fingering weight yarns, which would be classed as 4-ply.
I can’t say I’ve ever seen “ply” listed on a yarn label, but I’m in the US.
Ply used to be very common in the UK to name yarn weights but probably not so much now.