s a physical object, a book is a stack of usually rectangular pages (made
of papyrus, parchment, vellum, or paper) oriented with one edge tied, sewn, or otherwise fixed
together and then bound to the flexible spine of a protective cover of heavier, relatively inflexible
material.[1] The technical term for this physical arrangement is codex (in the plural, codices). In
the history of hand-held physical supports for extended written compositions or records, the
codex replaces its immediate predecessor, the scroll. A single sheet in a codex is a leaf, and
each side of a leaf is a page.
As an intellectual object, a book is prototypically a composition of such great length that it takes a
considerable investment of time to compose and a still considerable, though not so extensive,
investment of time to read. This sense of book has a restricted and an unrestricted sense. In the
restricted sense, a book is a self-sufficient section or part of a longer composition, a usage that
reflects the fact that, in antiquity, long works had to be written on several scrolls, and each scroll
had to be identified by the book it contained. So, for instance, each part of Aristotle's Physics is
called a book, as of course the Bible encompasses many different books. In the unrestricted
sense, a book is the compositional whole of which such sections, whether called books or
chapters or parts, are parts.
The intellectual content in a physical book need not be a composition, nor even be called a book.
Books can consist only of drawings, engravings, or photographs, or such things as crossword
puzzles or cut-out dolls. In a physical book the pages can be left blank or can feature an abstract
set of lines as support for on-going entries, i.e., an account book, an appointment book, a log
book, an autograph book, a notebook, a diary or day book, or a sketch book. Some physical
books are made with pages thick and sturdy enough to support other physical objects, like a
scrapbook or photograph album. Books may be distributed in electronic form as e-books and
other formats.