A subwriter is a person who writes part of a book, movie, or other work, but not the whole thing.
Subwriters are important for making big works, but they might not get as much attention as the main writer.
Examples:
The subwriter helped write the story.
The subwriter is not the main writer.
The subwriter wrote some of the words in the book.
The subwriter is like a helper writer.
The subwriter wrote the exciting part of the movie.
The subwriter's name is not on the front of the book.