A quarto, abbreviated as q, is a large book or pamphlet made from one or more sheets of paper folded once and cut to form four leaves (eight pages). It is named as such since it is one-fourth the size of a whole sheet.
Quartos were commonly used in England between 1500 and 1650 when they started being replaced by octavos. The term distinguishes such books from smaller (“octavo”) and more oversized (“folio”) products; see paper sizes for additional details. Many of William Shakespeare’s plays first appeared in this edition.
Some of his texts exist only in quartos; anything that survives in complete form from this period was almost certainly printed in folio or otherwise superseded by later edition(s); most still need to be updated for their initial publication.
In printing and publishing, “quarto” is also a technical term. It refers to a piece of paper folded once to make four pages, which can then be cut down into four pages, each one-quarter the size of the original full sheet.
The term “quarto” can also refer to book formats in general. A quarto book usually comprises four leaves (eight pages), each one-quarter the size of a standard page. Consequently, such a book typically measures around 9 inches by 6 inches (23 cm by 15 cm). It’s a format often used for brochures, small books, or pamphlets. Certain types of magazines use this format, too – The New Yorker is an example.