quarto
/ˈkwɔːtəʊ/(缩略词： 4 to)
noun
(pl. -os)［mass noun］
1- Printing a size of book page resulting from folding each printed sheet into four leaves (eight pages)【印刷】四开。
1.1
- count noun a book of this size四开本书。
1.2
- a size of writing paper, 10 in. ×8in. (254×203 mm)四开书写纸。
词源
late 16th cent.: from Latin （in） quartot '(in) the fourth (of a sheet)'， ablative of quartus 'fourth'.