n. pl. twelve·mos
American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.


n, pl -mos
(Printing, Lithography & Bookbinding) bookbinding another word for duodecimo
Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014


(ˌdu əˈdɛs əˌmoʊ, ˌdyu-)

n., pl. -mos,
adj. n.
1. a book size of about 5 x 7½ in. (13 x 19 cm), determined by printing on sheets folded to form 12 leaves or 24 pages. Symbol: 12 mo, 12°
2. a book of this size.
3. in duodecimo; twelvemo.
Also called twelvemo.
[1650–60; short for Latin in duodecimō in twelfth]
Random House Kernerman Webster's College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.
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References in periodicals archive ?
The title page of his 1652 English Physitian specifies that it cost three pence, the same price as the rate of sending a letter by domestic post in 1657; while the 1654 twelvemo edition of Culpeper's translation of th Pharmacopoeia, called the London Dispensatory, claims that "its Price may not exceed the poores purse." (43) His strategy worked: The English Physician was published in over 100 subsequent editions, including fifteen before 1700, while the 1720 Boston edition of Culpeper's London Dispensatory was the first full-length medical book published in the colonies.
(59) Of these, the lengthiest, and therefore the most costly, were Edwards's Discourses on Various Important Subjects (286 pages; octavo) and Some Thoughts Concerning the Present Revival of Religion in New-England (378 pages; twelvemo).
(twelvemo., 12mo.) Usually derived from a sheet folded so as to yield twelve page sheets.