Appendix:Latin third declension

Nouns

Description

Latin nouns of the third declension have genitive singular forms in -is. The nominative and vocative singular forms are identical to each other, and are often quite different from other cases: thus it is common to refer to third-declension nouns using two citation forms, the nominative singular and genitive singular, separated by a comma, e.g. rādīx, rādīcis f (“root”). This declension includes nouns of all three genders.

The third declension includes both nouns that originally had a stem ending in a consonant, and nouns that originally had a stem ending in the vowel i (as seen for example in the neuter genitive plural animalium). By Classical Latin, these two etymologically distinct categories had become confused, and in a number of cases, conflated: as a result, in addition to 'pure' consonant-stem and i-stem inflection, many third-declension nouns display 'mixed' patterns of declension.

Words borrowed from Greek's third declension are inflected with a varying mixture of Greek and Latin case endings.

General endings

Third declension endings

Case	Singular		Plural
	m./f.	n.	m./f.	n.
nominative	-s / -ēs / -is	-∅ -e	-ēs	-a -ia
genitive	-is		-um -ium
dative	-ī		-ibus
accusative	-em (-im)	-∅ -e	-ēs (-īs)	-a -ia
ablative	-e (-ī)		-ibus
vocative	-s / -ēs / -is	-∅ -e	-ēs	-a -ia
locative	-ī (-e)		-ibus

• Students of Latin are typically taught to memorize the nominative singular form of a third-declension noun as a stem of its own. Non-neuter nouns normally end in -s in the nominative singular, but this suffix frequently causes additional changes in form, as when it combines with a preceding -c- /k/ or -g- /ɡ/ to form -x /ks/ (as in vōx, vōcis or rēx, rēgis). Other endings can also be seen, such as -ō in non-neuter n-stem nouns (e.g. homō, hominis).
• Certain endings have consonant-stem and i-stem variants. I-stem nouns regularly have a nominative/accusative neuter plural in -ia and a genitive plural in -ium. Masculine and feminine i-stem nouns commonly formed their accusative plural in -īs up through Classical Latin, but it eventually became common in later Latin to replace this with the variant form -ēs. The ablative singular in -ī is found in i-stem neuter nouns and a relatively small number of "pure" i-stem masculine or feminine nouns. The accusative singular in -im is also a feature of "pure" non-neuter i-stems. Most non-neuter i-stem nouns instead display a 'mixed' declension pattern with singular forms like those of a consonant stem (an ablative singular in -e and an accusative singular in -em) alongside i-stem plural forms.

Parisyllables and Imparisyllables

Nouns are called "parisyllabic" if they have the same number of syllables in the nominative and genitive singular (e.g. the nom. civis and gen. civis both have two syllables). Nouns are called "imparisyllabic" if they have different numbers of syllables in the nominative and genitive singular (e.g. the nom. consul and gen. consulis have two and three syllables, respectively).

• Non-neuter parisyllabic nouns tend to show i-stem plural endings, whereas non-neuter imparisyllabic nouns tend to show consonant-stem plural endings, but there are a number of exceptions. In some "imparisyllabic" nouns, the genitive plural nonetheless ends in "-ium": lis, litis; dos, dotis; mus, muris; etc.
• Certain parisyllabic nouns show 'pure' i-stem inflection with an accusative singular in "-im" and an ablative singular in "-i": turris,-is; puppis, -is; sitis, -is; vis, -is; tussis, -is; securis, -is; febris, -is.

Neuter nouns follow a different rule. Rather than counting the syllables, neuter third-declension nouns tend to be pure i-stem if the nominative singular ends either in -e, or in -al or -ar with a genitive singular in -ālis/-āris. (Historically, these nominative singular forms in -al or -ar developed from shortening of original -āle or -āre.) Otherwise, neuter third-declension nouns tend to be pure consonant-stems.

• For example, "animal, -is" and "calcar,-is" inflect with i-stem endings.

Examples

Imparisyllabic consonant stem

Citation form: homō, hominis m

Case	Singular	Plural
nominative	homō	homin·ēs
genitive	homin·is	homin·um
dative	homin·ī	homin·ibus
accusative	homin·em	homin·ēs
ablative	homin·e	homin·ibus
vocative	homō	homin·ēs

Neuter consonant stem

Citation form: nōmen, nōminis n

Case	Singular	Plural
nominative	nōmen	nōmin·a
genitive	nōmin·is	nōmin·um
dative	nōmin·ī	nōmin·ibus
accusative	nōmen	nōmin·a
ablative	nōmin·e	nōmin·ibus
vocative	nōmen	nōmin·a

Parisyllabic i-stem

Citation form: turris, turris f

Case	Singular	Plural
nominative	turris	turrēs
genitive	turris	turrium
dative	turrī	turribus
accusative	turrem (-im)	turrēs (-īs)
ablative	turre (-ī)	turribus
vocative	turris	turrēs

Neuter i-stem

Citation form: animal, animālis n

Case	Singular	Plural
nominative	animal	animālia
genitive	animālis	animālium
dative	animālī	animālibus
accusative	animal	animālia
ablative	animālī	animālibus
vocative	animal	animālia

Mixed declension (mixed i-stem)

Citation form: nox, noctis f

Case	Singular	Plural
nominative	nox	noctēs
genitive	noctis	noctium
dative	noctī	noctibus
accusative	noctem	noctēs
ablative	nocte	noctibus
vocative	nox	noctēs

Greek declensions

Declension general

Citation form: āēr, āeris m, sometimes f

Case	Singular	Plural
nominative	āēr	āer·ēs
genitive	āer·is / āer·os	āer·um
dative	āer·ī	āer·ibus
accusative	āer·a / āer·em	āer·ēs
ablative	āer·e	āer·ibus
vocative	āēr	āer·ēs

Citation form: tigris, tigridis m and f

Case	Singular	Plural
nominative	tigris	tigr·ēs / tigrid·ēs
genitive	tigrid·is / tigr·is / tigrid·os	tigr·ium
dative	tigrid·ī / tigr·ī	tigr·ibus
accusative	tigr·im / tigr·in	tigr·is / tigrid·as
ablative	tigrid·e / tigr·ī	tigr·ibus
vocative	tigris	tigr·ēs / tigrid·ēs

Similiar to i-stem declension:

Case	Singular	Plural
nominative	-is	-es
genitive	-is; -os; -eos	-ium; -eon
dative	-i	-ibus
accusative	-im; -in	-is, -es; -eis
ablative	-i	-ibus
vocative	-is	-es

Examples:

• haeresis, -eos, f.; basis, -is and -eos, f.; tigris, -is, m. and f.

For feminine proper nouns from Greek in -ō with genitive in -ūs, see Appendix:Latin fourth declension § Feminine -ō form (from Greek).

Five types of third-declension Greek nouns

Excluding proper nouns, there seem to be around 4-5 types of declensions of Greek nouns as part of Latin's 3rd declension:

1. in -ō, like ēchō, -ūs, f.

• Genitive singular -ūs, all other singular cases -ō. Unlike Latin third-declension nouns, which eventually came to have short -ŏ the nominative/vocative singular, the -ō in Greek nouns was always long.
• Not used in the plural.
• echo is said to be in 3rd declension - not in 4 as it's here at Wiktionary.
• Georges mentions acc. sg as -ōn for êchô.
• It might also be -ōnis, -ōnī, -ōnem, -ōne (gen., dat., acc., abl. sg.), like the proper noun Dīdō, which was sometimes adapted and inflected like a native Latin third-declension word with a genitive singular in -ōnis.

2. chaos, epos, melos - n.

• It's commonly said that some cases are missing or were missing in antique times.

Case	n.
Singular
Nom.	-os
Gen.	-i; -us
Dat.	-o; -i
Acc.	-os
Abl.	-o
Voc.	-os
Plural
Nom.	-ē (-ea)
Gen.	-um
Dat.	-ibus
Acc.	-ē
Abl.	-ibus
Voc.	-ē

There are 3 declension variants: 1. more like Greek declension; 2. influenced by Latin's second declension and 3. changed to masculine words like Latin's second declension (e.g. cētus, -i, m. from cētos, -us, n. = (τό) κῆτος).

3. chelys (f.)

• It is similar to the variant that is similar to i-stem declension (see below), but often without i, e.g.: acc.sg. as -n instead of -in added to chely-, or acc.sg. as -yn instead of -in added to chel-.
• Instead of e.g. -ibus in dat.&abl. pl. it might also be chelybus (Lewis Marcus).
• Somewhere forms like chelin instead of chelyn were mentioned.

4. Like i-declension

Case	m./f.
	Singular
Nom.	-is
Gen.	-is; -eos, -ios
Dat.	-ī
Acc.	-im; -in
Abl.	-ī
Voc.	-is (-i)
Case	Plural
Nom.	-ēs
Gen.	-ium; -eōn
Dat.	-ibus
Acc.	-īs, -ēs
Abl.	-ibus
Voc.	-ēs

• Vowel lengths: Gen. sg.: In older English works (A&G, L&S) it is -eōs instead of -eos. Allen & Greenough and Lewis & Short have -eōs; Lewis Marcus, Georges, Pons have -eos. As Georges and Pons are newer than A&G and L&S, it seems more reliable (cf. stēlla, as opposed to stella).
• Examples: haeresis, basis (acc. pl. also -e͡is and accourding to Lewis Marcus with other irregular forms), tigris (gen. sg. -is), poēsis (poësis)

5. Like consonantic declension

Cases	m./f.	or ys, m./f.	n.
	Singular
Nom.	~(s)/~(ēr)/~(n)	~(ys)	-a
Gen.	-is; -os ‡¹
Dat.	-ī; (-i)
Acc.	-em; -a		-a
Abl.	-e
Voc.	~(s)/~(ēr)/~(n)	(~ys), -y	-a
Kasus	Plural
Nom.	-ēs; -es		-a
Gen.	-um		-um & -orum
Dat.	-ibus; ‡²		-ibus & -is
Acc.	-ēs; -as (-es) ‡³		-a
Abl.	-ibus; ‡²		-ibus & -is
Voc.	-ēs; -es		-a

• ‡¹ (especially) by words with gen. sg. in dis it is also dos
• ‡² a) Accourding to Lewis Marcus some words have the ending is resp. -isi and -ibus, e.g. heroisi from heros. b) Weyh writes that dat. pl. can be -si and -sin (example: ethesi), and Georges and Lewis & Short have abl. pl. ethesin of ēthos. "herosi" can be found, it's e.g. in Prisciani Caesariensis Grammatici Opera ("non herosi [...] herosi"). c) ἥρως is like herosi[n] in dat. pl. Thus -si[n] in dat. and abl. pl. makes sense, but heroisi seems wrong. -- Maybe pure Greek declensions (in singular and plural) + (old) transcription into Latin should be added, so one can see what might be possible. (?)
• ‡³ (at least) some words have -es and -ēs/-as
• Words of neuter gender have forms of the 3rd and of the 2nd declension in plural. Well, poēma/poëma has those forms, but that could also be an exception.

Examples:

• hērōs, adamās (also adamāns), lebēs (Greek-like acc. pl. with -es and -as)
• lampas (Greek-like acc. pl. with -es and -as), tigris (-idis; having the forms of tigris, -is in gen. sg. and nom., gen., dat. and abl. pl.), delphīn (also delphīs)
• pēlamys, chlamys
• crāter, āēr
• poēma (poëma), n.

Locative

The use of the locative case in Latin is highly restricted: it is used for city names, some island names, and a handful of common nouns, but is not used for the vast majority of common nouns. As in all declensions, plural nouns that can be used in the locative (chiefly consisting of plurale tantum proper nouns) take the same endings as the plural dative/ablative: thus, for Trallēs the form Trallibus is used as a locative.

Singular third-declension nouns that can be used in the locative may take the ending -ī, as in rūrī from rūs or Carthāginī from Carthāgō, but ablative singular forms in -e, such as Carthāgine, can also be found used with the same sense.

Adjectives

Description

Latin nouns of the third declension comprise consonant stems and i-stems. The consonant stems include the comparative form of adjectives. This declension is divided into three subcategories: adjectives of one termination (which includes present participles), adjectives of two terminations (one for m and f, and one for n), and adjectives of three terminations (which are generally -er m, -ris f and -re n).

Examples

One-termination consonant stem

Citation form: vetus, -eris

Case	m f singular	n singular	m f plural	n plural
nominative	vetus	vetus	veter·ēs	veter·a
genitive	veter·is	veter·is	veter·um	veter·um
dative	veter·ī	veter·ī	veter·ibus	veter·ibus
accusative	veter·em	vetus	veter·ēs	veter·a
ablative	veter·e	veter·e	veter·ibus	veter·ibus
vocative	vetus	vetus	veter·ēs	veter·a

One-termination i-stem

Citation form: atrōx, -ōcis

Case	m f singular	n singular	m f plural	n plural
nominative	atrōx	atrōx	atrōc·ēs	atrōc·ia
genitive	atrōc·is	atrōc·is	atrōc·ium	atrōc·ium
dative	atrōc·ī	atrōc·ī	atrōc·ibus	atrōc·ibus
accusative	atrōc·em	atrōx	atrōc·ēs, ·īs	atrōc·ia
ablative	atrōc·ī	atrōc·ī	atrōc·ibus	atrōc·ibus
vocative	atrōx	atrōx	atrōc·ēs	atrōc·ia

Two-termination consonant stem (comparatives)

Citation form: melior, -us

Case	m f singular	n singular	m f plural	n plural
nominative	melior	melius	meliōr·ēs	meliōr·a
genitive	meliōr·is	meliōr·is	meliōr·um	meliōr·um
dative	meliōr·ī	meliōr·ī	meliōr·ibus	meliōr·ibus
accusative	meliōr·em	melius	meliōr·ēs	meliōr·a
ablative	meliōr·e	meliōr·e	meliōr·ibus	meliōr·ibus
vocative	melior	melius	meliōr·ēs	meliōr·a

Two-termination i-stem

Citation form: tristis, -e

Case	m f singular	n singular	m f plural	n plural
nominative	trist·is	trist·e	trist·ēs	trist·ia
genitive	trist·is	trist·is	trist·ium	trist·ium
dative	trist·ī	trist·ī	trist·ibus	trist·ibus
accusative	trist·em	trist·e	trist·ēs, -īs	trist·ia
ablative	trist·ī	trist·ī	trist·ibus	trist·ibus
vocative	trist·is	trist·e	trist·ēs	trist·ia

See also

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