[*] 71. Mixed i-stems have -em in the accusative and -e in the ablative singular, -ium in the genitive1 and -īs or -ēs in the accusative plural. They include the following:—
- Nouns in -ēs, gen. -is.2
- Monosyllables in -s or -x preceded by a consonant: as, ars , pōns, arx .
- Polysyllables in -ns or -rs: as, cliēns , cohors .
- Nouns in -tās, genitive -tātis (genitive plural usually -um)3: as, cīvitās .
- Penātēs, optimātēs , and nouns denoting birth or abode (patrials) in -ās, -īs, plural -ātēs, -ītēs: as, Arpīnās , plural Arpīnātēs;Quirīs, plural Quirītēs .
- The following monosyllables in -s or -x preceded by a vowel: dōs, fraus , glīs, līs , mās,mūs, nix, nox , strix, vīs .