|§ 269. Greek Nouns.—A few Greek Nouns in -ōs, mostly geographical, belong to this declension, and sometimes make Acc. in -ŏn instead of -um, as Dēl-ŏs, A. Dēl-ŏn (-um in prose).
|§ 270. Words ending in' -vus (and -ŭus), -vum (and -uum).—In the earlier Latin [see §259(1) ]these often have -ŏs instead of -ŭs, and -om instead of -um in the Nom. and Ace. Sing.
Thus Nom. ĕqu-ŏs a horse, Acc, ĕqu-om; N., salv-ŏs (m.) safe. Ace, salv-om; Nom. M. mortu-ŏs dead, Neut. mortŭ- om. [cu is often written for quu, as ĕcus, A. ĕcum.]
Third Declension.
§ 271. Acc. Sing, in -im.—Some Nouns with Nom. in -ĭs have -im instead of -em in Acc. Sing. Thus :
(a) Names of Rivers as Tĭbĕrĭm; Greek proper names as Neāpŏlim, Phălărim; and names of Animals and some other words taken from the Greek, as tigrim tiger, băsim 'pedestal.
(b) The following regularly:
sĭtim, tussira, vim, sĕcurirm,[1] puppim,[1] turrirm,[1] also būrim.[2]
Sometimes other Nouns :
In febris[3] oft; but seldom nāvis, sēmentis, pelvis, restis, clāvis.[4]
§ 272. Abl. Sing, in -ī.—Some.Nouns have an Abl. Sing, in -ī answering to the Acc. in -im. It is rarely found outside of Nouns in -ĭs. We have it regularly in:
tussī, vī, sĕcurī, canālī, sĭtī, strĭgĭlī, with sodālī.[5]
Further it appears in the following words (those in italics having it rarely):
fūstis, febris, turris, nāvis, puppis, pelvis, cīvis, clāvis, sēmentis, īgnis, amnis, orbis, anguis, unguis, clāssis, corbis, With bĭlls, fĭnis: frequently In imbrĭ, sŭpellēctĭlī.[6]
