There are at least 2 kinds of trunk. A large, full-grown tree that could be able to be processed into lumber. And a smaller one, the size of branch of the full grown tree, but larger than a twig, that would be used as fence or pole or many products as-is without much processing.
I would call the large one as a log, in my opinion if it was thicker than human body it is surely a log. But I got uncomfortable calling the small sized ones logs, especially if they're around the size of a human leg. But it is still a trunk and not a branch so I couldn't call it a branch, right?
Does English have specific terms for these differences?