This discussion won't resolve anything, but it may provide some entertainment.
When we share our work, we are inevitably required to describe the piece we've created, but there are times when the definition of shape a particular is up for debate. For example, at what point does a closed form become a hollow form? To my way of thinking, a "hollow form" is an urn-shaped vessel with an opening of less than one-quarter of the diameter, but I bet other people would define that differently. Inversely, in my world a "closed form" has an opening of more than half of the diameter, but there probably a bit of disagreement about that.
I also admit to feeling unsettled about calling certain pieces "boxes" versus "lidded jars/bowls." I always thought boxes were square items, so I prefer the latter description. And if I've created a closed form per the description in the previous paragraph but add a lid, does it suddenly become a "box?" Is an urn with a cap a "box," as well?
Now, I know some of you will say "who cares?" but the nomenclature surrounding our art can be muddley.