Well, as it is said in the title of my question, I'm wondering what the adjective and adverb of content are. Similarly, we have context whose adjective and adverb are contextual and contextually respectively, but what about content?
I guess you are not asking about the verb content. If you are, then they would be contented and contentedly.
I am quite sure you are asking about the noun content, like the nutritional content of milk, the news content of newspaper, the story content of a book, etc.
The adjective would be content-related. For example,
- He asked me contextual questions about the book.
- He asked me content-related questions about the book.
The adverb would content-wise. For example,
He spoke contextually about Paul's admonishment that women kept quiet, but asked their husbands at home.
He spoke content-wise about his recent book on Paul's admonishments for women.
Probably it's will be the following adjective in use
to be contained in
Content means there will be something in it. Something is being contained by something.