folio

thumb|upright=1|The title-page of the Shakespeare First Folio, 1623 thumb|Single folio from a large Qur'an, North Africa, 8th c. (Khalili Collection)

The term "folio" () has three interconnected but distinct meanings in the world of books and printing: first, it is a term for a common method of arranging sheets of paper into book form, folding the sheet only once, and a term for a book made in this way; second, it is a general term for a sheet, leaf or page in (especially) manuscripts and old books; and third, it is an approximate term for the size of a book, and for a book of this size.