That grammar evolves naturally, like species do, so any rules we find for the categorization of either should reflect reality, not try to dictate it.
For example, I just started that bit with a clause, which means it’s a fragment, not a sentence. I still put a period at the end of it and started it without any lead in, which is “wrong,” but it’s more that the rule is wrong, because what I wrote plays the role of a sentence in this case.
That grammar evolves naturally, like species do, so any rules we find for the categorization of either should reflect reality, not try to dictate it.
For example, I just started that bit with a clause, which means it’s a fragment, not a sentence. I still put a period at the end of it and started it without any lead in, which is “wrong,” but it’s more that the rule is wrong, because what I wrote plays the role of a sentence in this case.