Appendix:Latin third declension

A small number of Greek neuter third-declension nouns ending in -ος, such as ἔπος (épos), were taken into Latin. Often only some cases are attested in ancient times; e.g. epos used only in the nominative and accusative singular; chaos used in Classical Latin only in the nominative/accusative singular and ablative singular chaō. The endings of the Latin second declension were also used to adapt nouns like this, sometimes with a change in gender to the masculine (e.g. cētus m from κῆτος n (kêtos)). Some Greek contracted neuter plurals in -η, such as μέλη, from μέλος (mélos), were taken into Latin as rare neuter plural forms in -ē, e.g. melē, cētē = κήτη.

The third declension includes some positive adjectives and all comparative adjectives.

Third-declension positive adjectives can be divided into the following three categories:

• two terminations: these adjectives have two distinct nominative singular forms: one ending in -is used for the masculine and feminine, and one ending in -e for the neuter.
• three terminations: these adjectives have three distinct nominative singular forms: the masculine ends in -er, the feminine ends in -ris, and the neuter ends in -re.
• one termination: these adjectives have only one nominative singular form shared between all genders. Present participles are included in this category.

Positive adjectives of two or three terminations regularly take i-stem endings in the ablative singular (-ī), genitive plural (-ium), and neuter nominative/accusative/vocative plural (-ia), and optionally in the masculine/feminine accusative plural (-īs, alongside consonant-stem (-ēs). Adjectives of one termination may show either i-stem or consonant-stem forms.

This category contains the majority of positive third-declension adjectives. A number of common suffixes form adjectives of two terminations, such as -īlis, -īle; -ālis, -āle; -āris, -āre; and -ēnsis, -ēnse.

Citation form: trīstis, trīste

This is a small category. The only difference from adjectives of two terminations is the masculine nominative/vocative singular form ending in -er. Often a masculine nominative/vocative singular form ending in -r·is is also attested: that is, many third-declension adjectives of three terminations can alternatively be declined as adjectives of two terminations. In addition, the nominative singular forms ending in -er are sometimes attested in the feminine.

The genitive plural typically uses the i-stem ending -ium, but a few words in this category have an attested genitive plural form with the consonant-stem ending -um. These consonant-stem forms are most often seen in contexts where the word is being used as a non-neuter noun, rather than as an adjective: for example, celerum occurs as the genitive of the masculine noun celerēs (the name of a certain Roman military unit), and volucrum occurs as the genitive of the feminine noun volucrēs (“birds, flying creatures”). However, some adjectival uses are also attested: volucrum can modify a masculine or feminine noun in poetry, functioning as a genitive plural of the adjective volucer, and celerum is used as an adjective by the Late Latin medical writer Caelius Aurelianus (modifying the feminine noun passiōnum) and by Servius the Grammarian, the Late Latin author of a commentary on Vergil (modifying or in apposition to the masculine noun equitum).

Citation form: ācer, ācris, ācre

The nominative singular form is shared between all three genders, and other forms are built on the oblique stem (found by subtracting -is from the genitive singular). Third declension adjectives of one termination can show various inflection patterns.

Some take the same endings as third-declension adjectives of two or three terminations, with a genitive plural in -ium, neuter nominative/accusative/vocative plural in -ia, an optional i-stem masculine/feminine accusative plural in -īs (alongside consonant-stem -ēs), and normally an i-stem ablative singular in -ī. These endings are used by:

• adjectives that end in -āx in the nominative singular and -ācis in the genitive singular (a fairly large category)
• Adjectives that end in -ōx, -ōcis or -īx, -īcis: atrōx, ferōx, vēlōx, fēlīx, pernīx (some alternative ablative singular forms, such as īnfēlīce (Catullus 68) and pernīce (Lucretius 2.635) are attested, potentially for metrical reasons).
• Multiplicative numerals ending in -plex, -plicis, e.g. simplex, duplex, triplex, multiplex
• Adjectives with the form of present participles in -ns, -ntis (see below).
• anceps, ancipitis and praeceps, praecipitis

A very small number are attested with consonant-stem endings throughout, such as vetus (although its ablative singular has an alternative form veterī).

Some others are used mostly in the masculine and feminine (sometimes as nouns and sometimes as adjectives) and may show consonant-stem endings in this context, but lack any attested neuter nominative/accusative/vocative plural (at least in Classical Latin). Examples are āles and caelebs. Sometimes a form that is missing in Classical Latin is used or mentioned by a later author.

Citation form: atrōx, atrōcis

Citation form: vetus, veteris

Present participles are all declined like one-termination adjectives with a nominative singular in -ns and an oblique stem in -nt-: they inconsistently take either i-stem endings or consonant-stem endings.

• For the genitive plural, the i-stem ending -ium is in general more usual. But the consonant-stem ending -um is also found, perhaps especially for participles used as nouns, such as parentum. (The grammarian Servius claims that this ending occurs in the masculine or feminine gender, but should not occur in the neuter, based on the alleged principle that a genitive plural ought not have fewer syllables than the nominative plural.^[2]) In poetry, use of the consonant-stem ending might be motivated by metrical considerations, since a form ending in -ntium could not be used in dactylic verse unless its final heavy syllable was elided into a word-initial light syllable, and this is an uncommon (so-called "harsh") type of elision. The consonant-stem ending has sometimes been printed as -ûm, based on a false hypothesis that it is a contraction of the more usual ending -ium (etymologically, the consonant-stem ending seems instead to be an archaism).
• For the neuter nominative/accusative/vocative plural, the i-stem ending -ia is usual. The consonant-stem ending -a is very rare, but is attested in a few cases, such as silenta and fluenta (in place of usual silentia, fluentia).
• For the ablative singular, both -e and -ī are used: forms in -e tend to be used in ablative absolute constructions, and more generally, in cases where a participle has verbal force; forms in -ī tend to be used as adjectives, but not exclusively so. Overall, the usage of -e and -ī in the ablative singular shows some degree of instability for many third-declension nouns, adjectives and participles and often does not follow strict or simple rules.

For some adjectives, certain gender/case/number combinations may be 'defective' (that is, never used, at least in Classical Latin texts).

Some third-declension adjectives of one termination seem to lack a neuter nominative/accusative/vocative plural form. Words of this type often take consonant-stem endings and are typically used either as nouns with masculine or feminine gender, or as adjectives modifying masculine or feminine nouns. Some are attested with adjectival function in combination with neuter nouns, but examples may be limited to cases where the same form is shared between all genders. In this situation, it may be difficult to say whether the word is being used as a true adjective (which by definition shares its gender with the modified noun) or whether it is grammatically a noun in apposition (which may disagree in gender, as in flūmine n Rhodanō m "the River Rhône").

An example is iuvenis:^[3] this can be used as a (usually masculine) noun 'youth, young man' or as an adjective 'young' (typically describing a man, less often a woman): in either case, it takes consonant-stem endings in its oblique forms, such as ablative singular iuvene or genitive plural iuvenum.^[4] It can be categorized as defective in gender because neuter forms, such as a nominative/accusative plural *iuvena, do not occur in Classical Latin. The similar word senex ('old man' rarely 'old woman', or as an adjective 'old, aged') likewise shows consonant-stem inflection and limited use in the neuter gender in Classical Latin: the form senibus, shared between all genders, is attested as a modifier of the neuter noun saeclīs in Ciris (a 1st-century poem from the Appendix Vergiliana), but distinct neuter forms such as a nominative/accusative plural *sena do not occur. (Missing forms of defective adjectives are sometimes created by analogy and used by postclassical authors; for example, in the case of iuvenis, an innovative i-stem neuter plural form iuvenia/juvenia is attested in Medieval Latin and New Latin.)

Words ending in -tor m and -trīx f, usually categorized as agent nouns, may be used adjectivally,^[5] with a similar sense to present participles.

• When forms ending in -tor are used this way, the inflection remains the same as that of the noun, with consonant-stem endings. The modified noun is normally grammatically masculine (although not necessarily animate).
  • Auctor alone can be used (both as noun and adjective) in the feminine as well as the masculine gender. There are also some examples where a form of auctor is used (either as an adjective or a noun in apposition) to modify a neuter noun, as in "cum ingenio n sibi auctore dignitatem peperissent" (Cicero De Oratore 1.198), "Italiam petiit fatis n auctoribus esto" (Vergil, Aeneid 10.67) and "Italiam si caelo n auctore recusas me pete" (Lucan, Bellum Civile 5.579)
• When forms ending in -trīx are used this way, the inflection is mostly the same as that of the noun, but some additional forms may be used following the i-stem inflection patterns of adjectives such as fēlīx. Thus, the word victrīx, when used as an adjective 'victorious', may have an ablative singular either in -e (victrīce) or in -ī (victrīcī). In the singular, such adjectives in -trīx are normally restricted to modifying feminine nouns, but in the plural, they also came to be used sometimes with neuter nouns, taking the i-stem endings -ia in the nominative/accusative/vocative plural and -ium in the genitive plural: thus, phrases such as 'victricia arma' and 'victricium armorum' can be used in Classical Latin.

The Greek endings -ᾰ́ς, -ᾰ́δος f (-ás, -ádos) and -ῐς, -ῐδος f (-is, -idos), used to form feminine adjectives from the names of locations or nations, were also used in Latin as endings of feminine adjectives or nouns (either in words taken as a whole from Greek, or in words formed by analogy).^[5]

Comparative adjectives nearly all follow the same declension pattern, showing a nominative singular in -ior for the masculine and feminine and a nominative singular in -ius for the neuter, with other forms built on a stem in -iōr- combined with consonant-stem endings (such as ablative singular -e, genitive plural -um, and neuter nominative/accusative/vocative plural -a). Alternative i-stem endings are occasionally found for the ablative singular (-ī) and the masculine/feminine accusative plural (-īs). The word plūrēs (plural-only when used as an adjective) shows a modified variant of this declension pattern.^[6]

Citation form: melior, melius

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