"He writes the word on the board."
If adverbials are simply about the verb, then “on the board” in “He writes the word on the board” can be explained as either an adverbial or an complement, for on the board simply describes writing.
But evidently, “on the board’ is a complement, not an adverbial. In my understanding, adverbials are more inclined to the subject and meanwhile very related to the verb. So “on the board” cannot be an adverbial, for if it is, it will mean the man is standing on the board.
However in most grammar books, adverbials are described as merely “modifying or defining the sentence or the verb”, no subject here. I mean can “modifying the verb” be understood as adverbials are inclined to the subject or not?