section_path: Definitions
section_name: Definitions
paragraph_text: Definitions
  
  In its modern incarnation, a book is typically composed of many pages (commonly of paper, parchment, or vellum) that are bound together along one edge and protected by a cover. By extension, book refers to a physical book's written, printed, or graphic contents. A single part or division of a longer written work may also be called a book, especially for some works composed in antiquity: each part of Aristotle 's Physics, for example, is a book.
  
  It is difficult to create a precise definition of the book that clearly delineates it from other kinds of written material across time and culture. The meaning of the term has changed substantially over time with the evolution of communication media. Historian of books James Raven has suggested that when studying how books have been used to communicate, they should be defined in a broadly inclusive way as "portable, durable, replicable and legible" means of recording and disseminating information, rather than relying on physical or contextual features. This would include, for example, ebooks, newspapers, and quipus (a form of knot-based recording historically used by cultures in Andean South America), but not objects fixed in place such as inscribed monuments.
  
  A stricter definition is given by UNESCO: for the purpose of recording national statistics on book production, it recommended that a book be defined as "a non-periodical printed publication of at least 49 pages, exclusive of the cover pages, published in the country and made available to the public", distinguishing them from other written material such as pamphlets. Kovač et al. have critiqued this definition for failing to account for new digital formats. They propose four criteria (a minimum length; textual content; a form with defined boundaries; and "information architecture" like linear structure and certain textual elements) that form a "hierarchy of the book", in which formats that fulfill more criteria are considered more similar to the traditional printed book.
  
  Although in academic language a monograph is a specialist work on a single subject, in library and information science the term is used more broadly to mean any non-serial publication complete in one volume (a physical book) or a definite number of volumes (such as a multi-volume novel), in contrast to serial or periodical publications.