[418]. Some substantives have different meanings in the two numbers: as,
aedis, temple, aedēs, house; auxilium, aid, auxilia, auxiliaries; carcer, jail, carcerēs, race-barriers; Castrum, Castle, castra, camp; comitium, meeting-place, comitia, election; cōpia, abundance, cōpiae, troops; facultās, ability, facultātēs, wealth; fīnis, end, fīnēs, boundaries; grātia, favour, grātiae, thanks; impedīmentum, hindrance, impedīmenta, baggage; littera, letter (of the alphabet), litterae, epistle; rōstrum, beak, rōstra, speakers stand. See also aqua, bonum, fortūna, lūdus, opera, pars, in the dictionary.
[CASE.]
[419]. Nouns have five cases, the Nominative, Genitive, Dative, Accusative, and Ablative.
The nominative represents a noun as subject, the accusative as object; the genitive denotes the relation of of, the dative of to or for, and the ablative of from, with, in, or by. But the meanings of the cases are best learnt from reading. All cases but the nominative and vocative ([420]) are called Oblique Cases.
[420]. Town names and a few appellatives have also a case denoting the place where, called the Locative. Masculine stems in -o- and some Greek stems with other endings have still another form used in addressing a person or thing, called the Vocative.
[421]. The stem of a noun is best seen in the genitive; in the genitive plural it is preserved without change, except that o of -o- stems is lengthened ([123]). In dictionaries the stem ending is indicated by the genitive singular, thus: -ae, -ī, -is, -ūs (-ĕī), indicate respectively stems in -ā-, -o-, a consonant or -i-, -u-, and -ē-, as follows:
| Genitive Singular. | Genitive Plural. | Stems in. |
|---|---|---|
| -ae, mēnsae, table | -ārum, mēnsā-rum | -ā-, mēnsā-, N. mēnsa |
| -ī, dominī, master | -ōrum, dominō-rum | -o-, domino-, N. dominus |
| -is, rēgis, king | -cons. um, rēg-um | -consonant, rēg-, N. rēx |
| -is, cīvis, citizen | -ium, cīvi-um | -i-, cīvi-, N. cīvis |
| -ūs, portus, port | -uum, portu-um | -u-, portu-, N. portus |
| (ĕ̄ī, rĕ̄ī), thing | (-ērum, rē-rum) | -ē, rē-, N. rēs |
[422]. Gender nominatives usually add -s to the stem: as, servo-s or servu-s, slave, rēx ([164, 1]), cīvi-s, portu-s, rē-s. But stems in -ā- or in a continuous consonant (-l-, -n-, -r-, or -s-) have no -s: as, mēnsa, cōnsul, consul, flāmen, special priest, pater, father, flōs, flower.
[423]. Neuters have the nominative and accusative alike; in the singular the stem is used: as nōmen, name; or a shortened stem: as, exemplar, pattern; but stems in -o- take -m: as, aevo-m or aevu-m, age. In the plural -a is always used: as, rēgna, kingdoms, nōmina, cornua, horns. For -s in adjectives ‘of one ending,’ see [612].