ăvis often has ăvi when it means omen.
Abl. of Adjectives in -is used as Nouns.—These form their Abl. sometimes in -ĕ, sometimes in -ī. The following regularly have -ī:
cōnsŭlaris ex-consul, fămĭliāris friend, gentīlis one of the same gens, trĭbūlis one of the same tribe, annālis m. annual (register), nātālis m. birthday; nōvālis f. fallow land, bĭpennis f. a two-headed axe.
Abl. Sing, in -ĕ instead of -ī.—The Parisyllabic Neuter rētĕ has Abl. rētĕ; mǎrĕ sea sometimes has Abl. mărĕ in poetry,
-ĕ have the following in -ar, far, baccar, nectar, and iŭbar.
Participles in -ns.—These generally have Abl. in -ĕ if used as Participles or Nouns, but -ī if used as Adjectives.
Thus tē sĕquentiĕ when you were following, a sequent^ interfectus killed by one who was following. But sĕquentī nocte on the following night.
§ 273. Acc. Plur. in -īs.—Nouns and Adjectives sometimes have an Acc. Plur. in -īs as well as -es. Thus nāv-īs, omnīs, trīs.
§ 274. Gen. Plur—The following Parisyllabic Nouns take -um, not -ĭum:
accĭpĭter, vŏlŭcris, iŭvĕnis, vātēsque, cănisque[1], et păter, et măter, frāter, sēdēsque, sĕnexque.[2]
ăpis bee, and mēnsis month vary.
The following Monosyllables, though Increasing, take -ium instead of -um: glīs, glīr-ium; vīs, vīr-ium; līs, līt-ium; mūs, mūr-ium; rēn kidney, usually rēn-ium; mās (adj.), măr-ium.
Several Nouns in -ās, -ātĭs (including optīmātēs, pĕnatēs which have no Sing.) have -ium as well as -um, as cīvitātium.
Participles in -ns, -ntis have -um, as well as the more usual -ium, especially in poetry. So also Nouns and Adjectives which are Participial in form; părēns parent almost always makes părentum.
§ 275. Greek Nouns.
Acc. Sing.—Many Proper and some Common Nouns,
