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

  • n. The page size of a book composed of printer's sheets folded into 16 leaves or 32 pages.
  • n. A book composed of sextodecimo pages.

from Wiktionary, Creative Commons Attribution/Share-Alike License

  • n. A size of a sheet of paper resulting from folding and cutting a sheet of paper into sixteenths (3.25"-5" x 5"-6.25").
  • n. A book consisting of pages of that size.

from the GNU version of the Collaborative International Dictionary of English

  • adj. Having sixteen leaves to a sheet; of, or equal to, the size of one fold of a sheet of printing paper when folded so as to make sixteen leaves, or thirty-two pages.
  • n. A book composed of sheets each of which is folded into sixteen leaves; hence, indicating, more or less definitely, a size of a book; -- usually written 16mo, or 16°.

from The Century Dictionary and Cyclopedia

  • n. A sheet of paper when regularly folded in 16 leaves of equal size; also, a pamphlet or book made up of folded sheets of 16 leaves: usually indicated thus, 16 mo or 16° (commonly read sixteenmo). Also used adjectively.


Latin sextōdecimō, ablative of sextusdecimus, one sixteenth : sextus, sixth; see s(w)eks in Indo-European roots + decimus, tenth (from decem, ten; see dekm̥ in Indo-European roots).
(American Heritage® Dictionary of the English Language, Fourth Edition)
From Latin ablative of sextusdecimus ("sixteenth") (Wiktionary)


  • Some think that we are too effete or somehow trying to be elite – but what if, instead of 16mo, 24mo, and 32mo we wrote sextodecimo, vigesimoquarto, and trigesimosecundo?

    biblio poetry - Dimensions

  • This series starts out bravely in Latin (quarto, octavo), but begins to falter a bit when it gets to 16mo (sextodecimo/sixteenmo), & finally tails off into English.

    On twoth

  • Sextodecimo, vellum binding, Batchelor Flower (2) paper, Golden type; 525 paper copies, 21 on vellum This was the only sextodecimo bound in vellum.

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  • This was the fi rst Kelmscott book printed in sextodecimo format and the four-line initial appeared in this title for the fi rst time.

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  • Usually pronounced "sixteenmo" and written as 16mo. In rare/antique book trade, a small-format book made from printed sheets folded four times to give 16 leaves (32 pages). Also used as a more general term to refer to very small (but not miniature books.

    February 20, 2007