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[doo-uh-des-uh-moh, dyoo-] /ˌdu əˈdɛs əˌmoʊ, ˌdyu-/
noun, plural duodecimos.
Also called twelvemo. a book size of about 5 × 7½ inches (13 × 19 cm), determined by printing on sheets folded to form 12 leaves or 24 pages. Symbol: 12 mo, 12°.
a book of this size.
in duodecimo; twelvemo.
Origin of duodecimo
1650-60; short for Latin in duodecimō in twelfth Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2018.
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Examples from the Web for duodecimo
Historical Examples
  • It was in the duodecimo form, and consisted of about three hundred pages.

  • Of Lintotts first duodecimo edition 2500 copies were quickly sold off.

    Prices of Books Henry B. Wheatley
  • The sizes of books had not yet all come to octavo or duodecimo.

    The Printed Book Henri Bouchot
  • Were it not for the riff-raff, that place would be a paradise in duodecimo.

    A Transient Guest Edgar Saltus
  • Her works have been published in eighty-four volumes, duodecimo.

    Lives of Celebrated Women Samuel Griswold Goodrich
  • duodecimo, black morocco, with and without flaps, gilt edges.

  • duodecimo, crimson cloth; decorated title and frontispiece, pp. 300.

  • Two good volumes in duodecimo might be made out of the two in folio.

  • No doubt this duodecimo book was much more convenient than the folio size Instructions.

    British Flags W. G. Perrin
  • When he paid his next visit, it so happened that one of these duodecimo disputants lay upon the table.

    Willing to Die Joseph Sheridan Le Fanu
British Dictionary definitions for duodecimo


noun (pl) -mos
Also called twelvemo. a book size resulting from folding a sheet of paper into twelve leaves Often written 12mo, 12°
a book of this size
Word Origin
C17: from Latin phrase in duodecimō in twelfth, from duodecim twelve
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
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Word Origin and History for duodecimo

1650s, from Latin in duodecimo (folded) "in a twelfth" of a sheet, from ablative of duodecimus "twelfth," from duodecim (see dozen). Often abbreviated 12mo.; a book in which each page is the twelfth part of the printer's sheet.

Online Etymology Dictionary, © 2010 Douglas Harper
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