[424]. Gender accusatives singular add -m to the stem: as, mēnsa-m, servo-m or servu-m, nāvi-m, ship, portu-m, die-m. The consonant stems have the ending -em: as, rēg-em; most substantive stems in -i- and all adjectives also drop -i- and take -em: as, nāv-em, trīst-em, sad. In the plural, gender stems add -s before which the vowel is long: as, mēnsā-s, servō-s, rēgē-s, nāvī-s or nāvē-s, portū-s, rē-s.
[425]. The ablative singular usually ends in the long vowel of the stem: as, mēnsā, dominō, nāvī, portū, rē. The ablative of consonant stems usually has -e (rarely -ī-, see [502]): as, patre, father; and that of substantive -i- stems has -e more commonly than -ī: as, nāve.
[426]. The ablative singular of -ā- and -o- stems ended anciently in -ād and -ōd respectively: as, PRAIDAD, PREIVATOD; that of consonant stems in -īd: as, AIRID, COVENTIONID. But -d is almost entirely confined to inscriptions and disappeared early ([149]).
[427]. The genitive plural adds -rum to -ā-, -o-, and -ē- stems: as, mēnsā-rum, dominō-rum, rē-rum; and -um to consonant stems, -i- stems, and -u- stems: as, rēg-um, cīvi-um, portu-um.
[428]. The dative and ablative plural are always alike: stems in -ā- and -o- take -is, which blends with the stem vowel ([400]): as, mēnsīs, dominīs; other stems have -bus, before which consonant stems are extended by i: as, rēgi-bus, nāvi-bus, portu-bus or porti-bus, rē-bus.
[429]. Some pronouns and a few adjectives have some peculiar case endings; see [618-694].
[430]. Many nouns are defective in case.
Thus, many monosyllables have no genitive plural: as, aes, copper, cor, heart, cōs, whetstone, dōs, dowry, ōs, face, pāx, peace, pix, pitch, rōs, dew, sāl, salt, lūx, light; many words have no genitive, dative, or ablative plural: as, hiemps, winter; especially neuters: as, fār, spelt, fel, gall, mel, honey, pūs, matter, rūs, country, tūs, frankincense. Many words in -tu- (-su-) have only the ablative ([235]). For -ē- stems, see [600]. Other words more or less defective are exlēx, exspēs, fās and nefās, īnfitiās, inquiēs, īnstar, luēs, nēmō, opis and vicis genitives, pondō and sponte ablatives, secus, vīs. Many adjectives ‘of one ending’ want the nominative and accusative neuter plural and genitive plural.
[431]. Some adjectives are altogether indeclinable: as, frūgī, thrifty, an old dative; nēquam, naughty, an old accusative; quot, how many; tot, so many; and most numerals ([637]). These adjectives are attached to any case of a substantive without varying their own forms.