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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. 2017.
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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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