Allen and Greenough's New Latin Grammar for Schools and Colleges
J. B. Greenough, G. L. Kittredge, A. A. Howard, Benj. L. D'Ooge, Ed.

[*] a. In numbers below 100, if units precede tens, et is generally inserted: duo et vīgintī; otherwise et is omitted: vīgintī duo .

[*] b. In numbers above 100 the highest denomination generally stands first, the next second, etc., as in English. Et is either omitted entirely, or stands between the two highest denominations: mīlle ( et ) septingentī sexāgintā quattuor , 1764.

[*] Note.--Observe the following combinations of numerals with substantives:—

1. ūnus et vīgintī mīlitēs , or vīgintī mīlitēs ( et ) ūnus, 21 soldiers.
2. duo mīlia quīngentī mīlitēs , or duo mīlia mīlitum et quīngentī, 2500 soldiers.
3. mīlitēs mīlle ducentī trīgintā ūnus, 1231 soldiers.

[*] c. After mīlia the name of the objects enumerated is in the genitive:

1. duo mīlia hominum, two thousand men. ¹
2. cum tribus mīlibus mīlitum, with three thousand soldiers.
3. mīlia passuum tria, three thousand paces (three miles).

[*] d. For million, billion, trillion, etc., the Romans had no special words, out these numbers were expressed by multiplication (cf. § 138. a).

[*] e. Fractions are expressed, as in English, by cardinals in the numerator and ordinals in the denominator. The feminine gender is used to agree with pars expressed or understood:—two-sevenths, duae septimae (sc. partēs ); three-eighths, trēs octāvae (sc. partēs ).

One-half is dīmidia pars or dīmidium .

[*] Note 1.--When the numerator is one, it is omitted and pars is expressed: onethird, tertia pars; one-fourth, quārta pars .

[*] Note 2.--When the denominator is but one greater than the numerator, the numerator only is given: two-thirds, duae partēs; three-fourths, trēs partēs , etc.

[*] Note 3.--Fractions are also expressed by special words derived from as, a pound: as, triēns, a third; bēs, two-thirds. See § 637.