A book's format refers to the shape and dimensions of the physical book. When browsing bookseller catalogs and listings on the Internet, the terms and abbreviations used to describe book sizes (8vo, 12mo, folio, quarto, etc.) can seem confusing at first, but this page will help define a super octavo from a royal octavo.

Essentially these terms are simply an explanation of the book's evolution from single sheets of paper into a completed book with printed pages. Each term defines how many times the initial piece of paper was folded to become pages.