[24]. Nouns ending in the Nominative Singular in -vus, -vum, -quus, exhibited two types of inflection in the classical Latin,—an earlier and a later,—as follows:—
| Earlier Inflection (including Caesar and Cicero). | |||
| Servos, m., slave. | Aevom, n., age. | Equos, m., horse. | |
| SINGULAR. | |||
| Nom. | servos | aevom | equos |
| Gen. | servī | aevī | equī |
| Dat. | servō | aevō | equō |
| Acc. | servom | aevom | equom |
| Voc. | serve | aevom | eque |
| Abl. | servō | aevō | equō |
Later inflection (after Cicero). SINGULAR. | |||
| Nom. | servus | aevum | equus |
| Gen. | servī | aevī | equī |
| Dat. | servō | aevō | equō |
| Act. | servum | aevum | equum |
| Voc. | serve | aevum | eque |
| Abl. | servō | aevō | equō |
1. The Plural of these nouns is regular, and always uniform.
Peculiarities of Inflection in the Second Declension.
[25]. 1. Proper names in -ius regularly form the Genitive Singular in -ī (instead of -iī), and the Vocative Singular in -ī (for -ie); as Vergílī, of Virgil, or O Virgil (instead of Vergiliī, Vergilie). In such words the accent stands upon the penult, even though that be short. Nouns in -ajus, -ejus form the Gen. in -aī, -eī, as Pompejus, Pompeī.
2. Nouns in -ius and -ium, until after the beginning of the reign of Augustus (31 B.C.), regularly formed the Genitive Singular in -i (instead of -iī); as,—
| Nom. | ingenium | fīlius |
| Gen. | ingénī | fīlī |
These Genitives accent the penult, even when it is short.
3. Fīlius forms the Vocative Singular in -ī (for -ie); viz. fīlī, O son!
4. Deus, god, lacks the Vocative Singular. The Plural is inflected as follows:—