1. (a.) Having twenty-four leaves to a sheet; as, a twenty-fourmo form, book, leaf, size, etc.

2. (n.) A book composed of sheets, each of which is folded into twenty-four leaves; hence, indicating more or less definitely a size of book whose sheets are so folded; -- usually written 24mo, or 24.

L Sexagesima boxcar dozen duodecimo eighty eleven fifteen fifty five and twenty fortnight forty four and twenty fourscore fourscore and ten fourteen half a hundred long dozen ninety nonagenarian octogenarian quindecennial quindecim quindecima quindene score septuagenarian seventy sexagenarian sexagenary sexagesimo-quarto sixteen sixteenmo sixty sixty-four sixty-fourmo teens thirteen thirty-two thirty-twomo threescore threescore and ten twelve twelvemo twenty twenty-five twenty-four twenty-fourmo two dozen two weeks twoscore