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°.
2.
a book of this size.
adjective
3.
in duodecimo; twelvemo.
Origin
1650-60; short for Latinin duodecimō in twelfth
Examples from the web for duodecimo
Folio books are the largest, quarto the next largest, and octavo and duodecimo follow in descending order.
British Dictionary definitions for duodecimo
duodecimo
/ˌdjuːəʊˈdɛsɪˌməʊ/
noun (pl) -mos
1.
Also called twelvemo. a book size resulting from folding a sheet of paper into twelve leaves Often written 12mo, 12°
2.
a book of this size
Word Origin
C17: from Latin phrase in duodecimō in twelfth, from duodecim twelve
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.