The term EXPERT ON MELVIL DEWEY can be summarized as a LIBRARIAN, which is a 9 letter word. A librarian is a professional who works in a library and is responsible for organizing and managing the library's collection of books and other materials. They also provide assistance to patrons in locating and using library resources. An expert on Melvil Dewey would be someone who has an extensive knowledge of the Dewey Decimal System, which was created by Melvil Dewey in 1876 and is still used today to organize library materials.