Another of the terms referring to page or book size, octavo refers to a standard printer's sheet folded four times, producing eight leaves, or sixteen pages. Other standard sizes include folio which is folded only once, quarto which is folded twice for four leaves, and duodecimo, folded in a specific pattern for twelve leaves or twenty four pages.

example of octavo printing

Because the practice was so standard, a contemporary standard sized hardback book or trade paperback book is still often referred to as an octavo, since this size of leaf averages between eight to ten inches tall.