from The American Heritage® Dictionary of the English Language, 4th Edition

  • n. The page size obtained by folding a whole sheet into four leaves.
  • n. A book composed of pages of this size.

from Wiktionary, Creative Commons Attribution/Share-Alike License

  • n. A size of paper (7.5"-10" x 10"-12.5")(190-254 x 254-312 mm). Formed by folding and cutting one of several standard sizes of paper (15"-20" x 20"-25")(381-508 x 508-635 mm) twice to form 4 leaves (eight sides).
  • n. A book size, corresponding to the paper size.

from the GNU version of the Collaborative International Dictionary of English

  • adj. Having four leaves to the sheet; of the form or size of a quarto.
  • n. Originally, a book of the size of the fourth of sheet of printing paper; a size leaves; in present usage, a book of a square or nearly square form, and usually of large size.

from The Century Dictionary and Cyclopedia

  • n. A size of book in which the leaf is one fourth of a described or implied size of paper.
  • Noting the size of a book in which a sheet makes four leaves: as, a quarto volume; being of the size or shape of the leaves of a quarto; as, quarto paper; a quarto edition.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

  • n. the size of a book whose pages are made by folding a sheet of paper twice to form four leaves


Short for Middle English (in) quarto, (in) the fourth part (of a sheet), from Medieval Latin (in) quārtō, from Latin, ablative of quārtus, fourth; see kwetwer- in Indo-European roots.
(American Heritage® Dictionary of the English Language, Fourth Edition)
From Latin quartus ("fourth") (Wiktionary)



Log in or sign up to get involved in the conversation. It's quick and easy.

  • From p. 24 of Patrick Leigh Fermor's "A Time to Keep Silence":

    Vellum-bound folios and quartos receded in vistas, and thousands of ancient and modern works on theology, canon law, dogma, patrology, patristics, hagiography, mysticism and even magic, and almost as many on secular history, art and travel.

    January 21, 2014

  • Not just any old sheet of paper.

    A size of paper (7.5"-10" x 10"-12.5"). Formed by folding and cutting a standard large sheet of paper (15"-20" x 20"-25") twice to form 4 leaves (eight sides).

    Paper sizes such as quarto, American quarto, octavo, 16mo etc. really only continue in North America. Most of elsewhere uses ISO paper sizes - A0, A1 etc. China of course has its own sizes.

    July 25, 2008

  • Also 4to. In printing and book collecting, a book of distinctly squarish shape made from printed sheets folded into quarters (giving eight pages). Also used in a general way to describe books about the size and shape of a modern standard telephone directory.

    February 25, 2008