This was totally new to me, but apparently they are the same as in English.
cardinal / numeral = 3 / 4 = three / fourths.
All fractions use the feminine gender nouns (as though partēs).
- 2/7 = duae septimae
- 3/11 = trēs ūndecimae
- 19/13 = ūndēvīgintī tertiae decimae
- 5/104 = quīnque centēnsimae quartae
Here’s one exception: fraction with 1 in the numerator
- 1/2 = dīmidia pars or dīmdium
- 1/3 = tertia pars
- 1/4 = quarta pars
- 1/6 = sexta pars
- 1/8 = octava pars
1/2 is altogether exceptional, but the rest of 1/x fractions all read neuter plural + pars
Ok, now here’s another exception:
When the fraction is x / x + 1, the fraction reads ordinal (agreeing with partēs) + partēs
- 2/3 = duae partēs
- 12/13 = duodecimae partēs
- 56/57 = quīnquāgēnsimae sextae partēs
But weight, there’s more! There are also a host of special nouns used to describe fractions of weight, coin value or land distribution. (A&G aren’t explicit if they can be used to measure other fractions—does anyone know?)
There are a lot of them. Sorry.
- 1/12 uncia, -ae
- 1/6 sextāns, -antis
- 1/4 quadrāns, -antis
- 1/3 triēns, -entis
- 5/12 quīncunx, -unctis
- 1/2 sēmis, -missis
- 7/12 septunx, -unctis
- 2/3 bēs or bēssis, bēssis
- 2/3 dōdrāns, -antis
- 5/6 dextāns, -antis
- 11/12 deunx, -unctis
- 12/12 as, assis
The Essential AG: 135e, 637