[450]. deus, god, is declined as follows: N. deus, G. deī, D. and Ab. deō, Ac. deum. Plural: N. deī, di͡i, commonly dī, G. deōrum or deŭm, D. and Ab. deīs, di͡is, commonly dīs, Ac. deōs.
[451]. (2.) Stems in -o- with the nominative in -r or in -āius, -ēius, or -ōius are declined as follows:
| Examples Stems | puer, boy, puero-, M. | ager, field, agro-, M. | Pompēius, Pompey, Pompēio-, M. |
|---|---|---|---|
| Singular | |||
| Nom. | puer, a (or the) boy | ager | Pompēius |
| Gen. | puerī, a boy’s, of a boy | agrī | Pompēī |
| Dat. | puerō, to or for a boy | agrō | Pompēiō |
| Acc. | puerum, a boy | agrum | Pompēium |
| Abl. | puerō, from, with, or by a boy | agrō | Pompēiō |
| Voc. | Pompēī, Pompe͡i | ||
| Plural | |||
| Nom. | puerī, (the) boys | agrī | Pompēī |
| Gen. | puerōrum, boys’, of boys | agrōrum | Pompēiōrum |
| Dat. | puerīs, to or for boys | agrīs | Pompēīs |
| Acc. | puerōs, boys | agrōs | Pompēiōs |
| Abl. | puerīs, from, with, or by boys | agrīs | Pompēīs |
SINGULAR CASES.
[452]. -us and -um were originally -os and -om. But -us was used in the earliest times, -um somewhat later, and both became prevalent between 218 and 55 B.C. ([107, c]). After u or v, however, the -os and -om were retained till toward 50 A.D. ([107, c]); also after qu; but -cus and -cum often displaced -quos and -quom ([157]): as, equos, equom, or ecus, ecum, horse; antīquos, antīquom, or antīcus, antīcum, ancient. In the vocative -e was always used, and is retained by Plautus in puere, thou boy.
[453]. Words in -rus with a long penult, as, sevērus, stern, and the following substantives with a short penult are declined like domimus ([449]):
erus, master
iūniperus, juniper
numerus, number
umerus, shoulder