Octavos is a term used to describe a book format when the page is folded in eight sections. However, there are different synonyms for this term that can be used interchangeably to discuss this book format. Some of the synonyms that can be used to describe octavos include 16mo, duodecimo, and sextodecimo, depending on the number of sections the page is folded in. Sextodecimo describes a book where the page has been folded in 16 sections, and duodecimo describes a book folded in 12 sections. 16mo is a term used for books that have been folded in 16 sections. Each of these terms can be used to describe the same book format as octavos, depending on the number of folds used.