Appendix:Latin fifth declension

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 fifth declension nouns are feminine except diēs (which was originally masculine, but came to be used in some circumstances as a feminine) and derivatives or compounds of diēs, such as merīdiēs.

Quinta declinatio est quae genitivum singularem per ⟨-e-⟩ et ⟨-ī⟩ separatas syllabas profert, et est generis feminini tantum, excepto uno, “diēs”, qui est generis incerti; ⟨-ē-⟩ autem quae est ante ⟨-s⟩, tunc in genitivo producta est quum nominativus singularis ⟨-ĭ-⟩ et ⟨-ēs⟩ fuerit, ut “seriēs → seriēī”; et tunc correpta est quum aliquam ante se habuerit consonantem, ut “fidēs → fidĕī”, “rēs → rĕī”. Verum haec quinta declinatio nominativum terminat uno modo; exit enim in ⟨-ēs⟩, ut “speciēs → speciēī”. Verum non quicunque nominativus genere feminino in ⟨-ēs⟩ fuerit terminatus necesse est ut quintae sit declinationis, sed nomen quod fuerit quintae declinationis necesse est ut nominativum singularem in ⟨-ēs⟩ habeat terminatum.

Other than diēs and rēs, most fifth declension nouns were unused or rare in the plural in Classical Latin, especially the genitive and dative/ablative plural.^[1][2]

• Genitive plural: aside from diērum and rērum, the form speciērum is used by some ancient authors, such as Apuleius Madaurensis (2nd century); Cicero mentions the form only to condemn it, saying fōrmārum would be better. Priscian cites faciērum from a fragment of a speech by Cato the Elder (“exempla earum facierum”).
• Dative/ablative plural: aside from diēbus and rēbus, the form speciēbus is used by some ancient authors, such as the jurist Gaius (Institutiones 2.79, 2nd century); Cicero mentions the form only to condemn it, saying fōrmīs would be better.
• Nominative and accusative plural forms in -ēs are attested somewhat more often (e.g. "effigiēs sacrae dīvum", "Aristotelēs prīmus speciēs quās paulō ante dīxī labefactāvit").

There is a closed set of locative singular forms in -ē, mainly temporal expressions derived from diēs: examples include hodiē, perendiē, prīdiē,^[1] postrīdiē. 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:

• diēs, diēī m or f
• speciēs, speciēī f

Ending in consonant + -ēs:

• rēs, reī f
• fidēs, fideī, f

• Latin first declension
• Latin second declension
• Latin third declension
• Latin fourth declension
• Wikipedia article on declension
• Wikipedia article on Latin declension