[English reading of 24mo or xxivmo, used as abbreviation of L. vicesimo quarto, after 12mo = duodecimo, etc.] The size of a book in which each sheet is folded into 24 leaves. So Twentymo [= 20mo or xxmo, for L. vicesimo], the size of a book in which each sheet is folded into 20 leaves.
1841. Savage, Dict. Print., 798. Twenty-Fourmo, a sheet of paper folded into twenty-four leaves, forty-eight pages, is termed twenty-fourmo. Twentymo, a sheet of paper folded into twenty leaves, forty pages, is termed twentymo.
1901. Eggleston, Transit Civiliz., iii. 128. The sizes and shapes … running all the way to twenty-fourmos.
