Editing Latin declension (section)

=== {{anchor|d3}} Third declension===
The third declension is the largest group of nouns. The nominative singular of these nouns may end in ''-a'', ''-e'', ''-ī'', ''-ō'', ''-y'', ''-c'', ''-l'', ''-n'', ''-r'', ''-s'', ''-t'', or ''-x''. This group of nouns includes masculine, neuter, and feminine nouns.

====Consonant stems====
The stem of a consonant-stem noun may be found from the genitive case by removing the ending ''-is''. For example, the stem of {{wikt-lang|la|pax|pāx, pācis}} {{abbr|f.|feminine}} 'peace' is ''pāc-,'' the stem of {{wikt-lang|la|flumen|flūmen, flūminis}} {{abbr|n.|neuter}} 'river' is ''flūmin-'', and the stem of {{wikt-lang|la|flos|flōs, flōris}} {{abbr|m.|masculine}} 'flower' is ''flōr-.''

Masculine, feminine and neuter nouns often have their own special nominative singular endings. For instance, many masculine nouns end in ''-or'' ({{wikt-lang|la|amor|amor, amōris}}, 'love'). Many feminine nouns end in ''-īx'' ({{wikt-lang|la|phoenix|phoenīx, phoenīcis}}, 'phoenix'), and many neuter nouns end in ''-us'' with an ''r'' stem in the oblique cases ({{wikt-lang|la|onus|onus, oneris}} 'burden'; {{wikt-lang|la|tempus|tempus, temporis}} 'time').

{| class="wikitable"
|+ Third declension paradigm<br />(consonant stems)
|-
! rowspan="2" |
! colspan="2" | Masculine &<br />feminine || colspan="2" | Neuter
|-
! Singular || Plural
! Singular || Plural
|-
! Nominative, Vocative
|(-s) || rowspan="2" | -ēs || rowspan="2" | —{{efn-lr|The nominative and accusative of neuter nouns are always identical.}} || rowspan="2" | -a
|-
! Accusative
| -em
|-
! Genitive
| -is || -um || -is || -um
|-
! Dative
| -ī || rowspan="2" | -ibus ||  -ī || rowspan="2" | -ibus
|-
! Ablative
| -e || -e
|-
! Locative
| ''Dat./Abl.'' || ''Dat.'' || ''Dat./Abl.'' || ''Dat.''
|}

{{notelist-lr}}

{| class="wikitable"
! rowspan="2" |
! colspan="2" | {{wikt-lang|la|dux|dux, ducis}}<br />leader {{abbr|m.|masculine}}
! colspan="2" | {{wikt-lang|la|virtus|virtūs, virtūtis}}<br />virtue {{abbr|f.|feminine}}
! colspan="2" | {{wikt-lang|la|nomen|nōmen, nōminis}}<br />name {{abbr|n.|neuter}}
|-
! Singular
! Plural
! Singular
! Plural
! Singular
! Plural
|-
! Nominative, Vocative
|dux || rowspan="2" | ducēs ||virtūs || rowspan="2" | virtūtēs || rowspan="2" | nōmen || rowspan="2" | nōmina
|-
! Accusative
| ducem || virtūtem
|-
! Genitive
| ducis || ducum || virtūtis || virtūtum || nōminis || nōminum
|-
! Dative
| ducī || rowspan="2" | ducibus || virtūtī || rowspan="2" | virtūtibus || nōminī || rowspan="2" | nōminibus
|-
! Ablative
| duce || virtūte || nōmine
|}

The locative endings for the third declension are ''-ī'' or ''-e'' (singular) and ''-ibus'' (plural), as in {{wikt-lang|la|rus|rūrī}} 'in the country' and {{wikt-lang|la|Tralles|Trallibus}} 'at Tralles'.<ref>Allen and Greenough. §80.</ref>

==== {{anchor|d3i}} Third declension ''i''-stem and mixed nouns ====
The third declension also has a set of nouns that are declined differently. They are called '''''i''-stems'''. ''i''-stems are broken into two subcategories: pure and mixed. Pure ''i''-stems are indicated by special neuter endings. Mixed ''i''-stems are indicated by the double consonant rule. Stems indicated by the parisyllabic rule are usually mixed, occasionally pure.
;Masculine and feminine
:'''Parisyllabic rule:''' Some masculine and feminine third-declension ''i''-stem nouns have the same number of syllables in the genitive and the nominative. For example: {{wikt-lang|la|navis|nāvis, nāvis}} ('ship'); {{wikt-lang|la|nubes|nūbēs, nūbis}} ('cloud'). The nominative ends in ''-is'' or ''-ēs''.
:'''Double consonant rule:''' The rest of the masculine and feminine third-declension ''i''-stem nouns have two consonants before the ''-is'' in the genitive singular. For example: {{wikt-lang|la|pars|pars, partis}} ('part').
;Neuter
:'''Special neuter ending:''' Neuter third-declension ''i''-stems have no rule. However, all of them end in ''-al'', ''-ar'' or ''-e''. For example: {{wikt-lang|la|animal|animal, animālis}} ('animal'); {{wikt-lang|la|cochlear|cochlear, cochleāris}} ('spoon'); {{wikt-lang|la|mare|mare, maris}} ('sea').

The mixed declension is distinguished from the consonant type only by having ''-ium'' in the genitive plural (and occasionally ''-īs'' in the accusative plural). The pure declension is characterized by having ''-ī'' in the ablative singular, ''-ium'' in the genitive plural, ''-ia'' in the nominative and accusative plural neuter, and ''-im'' in the accusative singular masculine and feminine (however, adjectives have ''-em'').

The accusative plural ending ''-īs'' is found in early Latin up to [[Virgil]], but from the early empire onwards it was replaced by ''-ēs''.<ref name=":0">Gildersleeve & Lodge (1895), p. 18.</ref>

The accusative singular ending ''-im'' is found only in a few words: always in {{lang|la|tussis}} 'cough', {{lang|la|sitis}} 'thirst', {{lang|la|Tiberis}} 'River Tiber'; usually in {{lang|la|secūris}} 'axe', {{lang|la|turris}} 'tower', {{lang|la|puppis}} 'poop', {{lang|la|febris}} 'fever'; occasionally in {{lang|la|nāvis}} 'ship'. Most nouns, however, have accusative singular ''-em''.<ref>Gildersleeve & Lodge (1895), p. 27.</ref> The ending ''-im'' is not found in any adjectives, even those that have a separate feminine such as {{lang|la|celeris}} 'swift' or {{Lang|la|ācris}} 'keen',<ref>Ernout, A. (1953), {{lang|fr|Morphologie historique du latin}}, p. 50.</ref> or in any masculine common nouns.

The ablative singular ''-ī'' is found in nouns which have ''-im'', and also, optionally, in some other nouns, e.g. {{lang|la|in ignī}} or {{lang|la|in igne}} 'in the fire'.

There are two mixed-declension neuter nouns: {{wikt-lang|la|cor|cor, cordis}} ('heart') and {{wikt-lang|la|os|os, ossis}} ('bone'). The mixed declension is also used in the plural-only adjective  {{wikt-lang|la|plures|plūrēs, plūra}} ('most').

{| class="wikitable"
|+ Third declension paradigm<br />(''i''-stem nouns)
|-
! rowspan="2" |
! colspan="2" | Masculine &<br />Feminine || colspan="2" | Neuter
|-
! Singular || Plural
! Singular || Plural
|-
! Nominative, Vocative
|— ||-ēs || rowspan="2" | — || rowspan="2" | -ia
|-
! Accusative
| -em<br />-im || -ēs<br />-īs
|-
! Genitive
| -is || -ium || -is || -ium
|-
! Dative
| -ī || rowspan="2" | -ibus || rowspan="2" | -ī || rowspan="2" | -ibus
|-
! Ablative
| -e<br />-ī
|-
! Locative
| ''Dat./Abl.'' || ''Dat.'' || ''Dat./Abl.'' || ''Dat.''
|}

{| class="wikitable"
|+ Third declension paradigm<br />(mixed nouns)
|-
! rowspan="2" |
! colspan="2" | Masculine &<br />Feminine || colspan="2" | Neuter
|-
! Singular || Plural
! Singular || Plural
|-
! Nominative, Vocative
|— ||-ēs || rowspan="2" | — || rowspan="2" | -a
|-
! Accusative
| -em || -ēs<br />-īs
|-
! Genitive
| -is || -ium || -is || -ium
|-
! Dative
| -ī || rowspan="2" | -ibus || -ī || rowspan="2" | -ibus
|-
! Ablative
| -e || -e
|-
! Locative
| ''Dat./Abl.'' || ''Dat.'' || ''Dat./Abl.'' || ''Dat.''
|}

{| class="wikitable"
! rowspan="3" |
! colspan="2" | {{wikt-lang|la|turris|turris, turris}}<br />tower {{abbr|f.|feminine}} (pure)
! colspan="2" | {{wikt-lang|la|pars|pars, partis}}<br />part, piece {{abbr|f.|feminine}} (mixed)
! colspan="2" | {{wikt-lang|la|animal|animal, animālis}}<br /> animal, living being {{abbr|n.|neuter}} (pure)
|-
! colspan="2" | Parisyllabic rule
! colspan="2" | Double consonant rule
! colspan="2" | Special neuter ending
|-
! Singular
! Plural
! Singular
! Plural
! Singular
! Plural
|-
! Nominative,  Vocative
|turris||turrēs ||pars ||partēs || rowspan="2" | animal || rowspan="2" | animālia
|-
! Accusative
| turrem<br />turrim || turrēs<br />turrīs || partem || partēs<br />partīs
|-
! Genitive
| turris || turrium || partis || partium || animālis || animālium
|-
! Dative
| turrī || rowspan="2" | turribus || partī || rowspan="2" | partibus || rowspan="2" | animālī || rowspan="2" | animālibus
|-
! Ablative
| turre<br />turrī || parte<br />(partī)
|}

The rules for determining ''i''-stems from non-''i''-stems and mixed ''i''-stems are guidelines rather than rules: many words that might be expected to be ''i''-stems according to the parisyllabic rule actually are not, such as {{wikt-lang|la|canis}} ('dog') or {{wikt-lang|la|iuvenis}} ('youth'), which have genitive plural {{lang|la|canum}} 'of dogs' and {{lang|la|iuvenum}} 'of young men'. Likewise, {{wikt-lang|la|pater}} ('father'), {{wikt-lang|la|māter}} ('mother'), {{wikt-lang|la|frāter}} ('brother'), and {{wikt-lang|la|parēns}} ('parent') violate the double-consonant rule. This fluidity even in Roman times resulted in much more uncertainty in Medieval Latin.

Some nouns in ''-tāt-'', such as {{wikt-lang|la|civitas|cīvitās, cīvitātis}} 'city, community' can have either consonant-stem or ''i''-stem genitive plural: {{lang|la|cīvitātum}} or {{lang|la|cīvitātium}} 'of the cities'.<ref name=":0"/>

==== Peculiarities ====
In the third declension, there are four irregular nouns.
{| class="wikitable"
|-
!rowspan="2" | Case
! colspan="2" | {{wikt-lang|la|vis|vīs, vīs}} <br /> force, power {{abbr|f.|feminine}}
! colspan="2" | {{wikt-lang|la|sus|sūs, suis}} <br /> swine, pig, hog {{abbr|m.f.|masculine and feminine}}
! colspan="2" | {{wikt-lang|la|bos|bōs, bovis}} <br /> ox, bullock {{abbr|m.f.|masculine and feminine}}
! {{wikt-lang|la|Iuppiter|Iuppiter, Iovis}} <br /> Jupiter {{abbr|m.|masculine}}
|-
! Singular || Plural || Singular || Plural || Singular || Plural || Singular
|-
! Nominative, Vocative
|vīs ||vīrēs ||sūs || rowspan="2" | suēs ||bōs{{efn-lr|name="ou"|Here ''ō'' or ''ū'' come from Old Latin ''ou''. Thus ''bō-/bū-'' and ''Iū-'' before consonant endings are alternate developments of the ''bov-'' and ''Iov-'' before vowel endings. — The double ''pp'' in the preferred form ''Iu-ppiter'' "Father Jove" is an alternate way of marking the length of the ''u'' in the etymological form ''Iū-piter'' (see footnote in [[Jupiter (mythology)]]). ''i'' is [[vowel reduction|weakened]] from ''a'' in {{wikt-lang|la|pater}} (Allen and Greenough, sect. 79 b).}} || rowspan="2" | bovēs ||Iuppiter<br />Iūpiter{{efn-lr|name="ou"}}
|-
! Accusative
| '''vim''' || vīrēs<br />vīrīs || suem || bovem || Iovem
|-
! Genitive
| vīs{{efn-lr|name="vis"|Genitive and dative cases are seldom used.}} || '''vīrium''' || suis || suum || bovis || '''boum'''<br />'''bovum''' || Iovis
|-
! Dative
| rowspan="2" | vī{{efn-lr|name="vis"}} || rowspan="2" | vīribus || suī || rowspan="2" | suibus<br />'''sūbus''' || bovī || rowspan="2" | '''bōbus'''<br />'''būbus'''{{efn-lr|name="ou"}} || Iovī
|-
! Ablative
| sue || bove || Iove
|}
{{notelist-lr}}