Latin nouns of the fifth declension end in -ēs in the nominative singular, with a genitive in -ēī (after -i-) or in -ĕī (after consonant), and have an invariable stem. Other than rēs, spēs, and fidēs, fifth-declension nouns generally end more specifically in -iēs. Some nouns show variation between fifth-declension forms in -iēs and first-declension forms in -ia.
All Latin words of the fifth declension are feminine except diēs (which was originally masculine, but came to be used in some circumstances as a feminine) and derivatives of diēs such as meridiēs.
| Case | Singular | Plural | |
|---|---|---|---|
| Stem in iēs |
-ēs | ||
| nominative | -ēs | -ēs | |
| genitive | -ēī | -eī | -ērum |
| dative | -ēī | -eī | -ēbus |
| accusative | -em | -ēs | |
| ablative | -ē | -ēbus | |
| vocative | -ēs | -ēs | |
Other than diēs and rēs, most fifth declension nouns are unused or uncommon in the plural. In particular, genitive plural forms other than diērum, rērum and dative/ablative plural forms other than diēbus, rēbus are rare, although some occur; nominative or accusative plural forms in -ēs are somewhat less rare.
There is a closed set of locative singular forms in -ē, mainly temporal expressions: examples include hodiē, perendiē, prīdiē. When used in isolation, forms like these can be analyzed as adverbs rather than nouns: however, their original status as locative-case nouns is shown by expressions that contain an agreeing adjective in the locative case. Aulus Gellius (Noctes Atticae 10.24) describes expressions such as "diequinti"/"diequinte" as compound adverbs ("adverbio copulate") and attributes their use to to the time of Cicero and his predecessors.
Ending in -iēs:
Ending in consonant + -ēs: