What is Octavo Size in Book Publishing?

Octavo (abbreviated as 8vo) is a book size. It is defined as a book that is 8 inches (203 mm) tall and has pages that are typically 5.5 inches (140 mm) wide. This size is commonly used for paperback books, and it is considered to be a popular size for mass-market paperbacks.
The term "octavo" comes from the Latin word "octavus," which means "eighth." This refers to the fact that an octavo book is one-eighth of a larger sheet of paper, such as a folio or a quarto. In the past, books were often printed on large sheets of paper that were folded to create smaller pages. The size of the page was determined by the size of the sheet of paper, and the size of the sheet was measured in terms of the number of times it could be folded (or "gathered") to create a book.
Octavo is just one of many sizes that are used for books, and there are many other sizes that are commonly used as well. Some other common book sizes include:
* Duodecimo (12mo): 6 inches tall and 3.5 inches wide
* Decimo (10mo): 7 inches tall and 4.5 inches wide
* Quartro (4to): 9 inches tall and 6 inches wide
* Folio (fo): 12 inches tall and 8 inches wide

Each of these sizes has its own unique characteristics, and they are used for different types of books and publications. For example, duodecimos are often used for mass-market paperbacks, while quartos are often used for more scholarly or academic works.