Third declension nouns
You can identify third declension nouns by their genitive singular ending ‘-is’.
You cannot identify third declension nouns in the nominative because they
- have various forms and spelling
- have endings that do not reveal their gender
- can be masculine, feminine or neuter
To decline a third declension noun:
- find the genitive singular, which will end ‘-is’
- remove the ‘-is’, leaving you with the stem
- add the endings shown below
Endings for Masculine and Feminine nouns
| Case | Singular | Plural |
| Nominative | various | -es |
| Vocative | same as nominative | -es |
| Accusative | -em | -es |
| Genitive | -is | -um |
| Dative | -i | -ibus |
| Ablative | -e | -ibus |
Look at our example of rex, regis (m.) king
| Case | Singular | Plural |
| Nominative | rex | reges |
| Vocative | rex | reges |
| Accusative | regem | reges |
| Genitive | regis | regum |
| Dative | regi | regibus |
| Ablative | rege | regibus |
Endings for Neuter nouns
| Case | Singular | Plural |
| Nominative | various | -a |
| Vocative | same as nominative | -a |
| Accusative | same as nominative | -a |
| Genitive | -is | -um |
| Dative | -i | -ibus |
| Ablative | -e | -ibus |
The genitive, dative and ablative endings are the same as for rex.
Handy hints
Remember, nominative and accusative cases of neuter nouns are always the same. The plural always ends in ‘a’.
Look at our example of jus, juris (n.) law, right
| Case | Singular | Plural |
| Nominative | jus | jura |
| Vocative | jus | jura |
| Accusative | jus | jura |
| Genitive | juris | jurum |
| Dative | juri | juribus |
| Ablative | jure | juribus |
Common third declension nouns:
| abbas, abbatis (m.) | abbot |
| etas, etatis (f.) | age |
| executor, executoris (m.) | executor |
| heres, heredis (m., f.) | heir |
| homo, hominis (m.) | man |
| miles, militis (m.) | knight |
| pater , patris (m.) | father |
| uxor , uxoris (f.) | wife |
You need to know the genitive case of a third declension noun, in order to decline it.
Therefore, both the nominative and genitive forms are provided in full in this series of lessons.
| curia domini Regis | the court of the lord king |
| Gregorius Basset et Johanna Hastings executores Willelmi Stuart sunt | Gregory Basset and Joanna Hastings are the executors of William Stuart |
These personal names decline like third declension nouns:
| Agnes, Agnetis | (f.) | Agnes |
| Johannes, Johannis | (m.) | John |
| Mathildis, Mathildis | (f.) | Matilda |
| Simo, Simonis | (m.) | Simon |
| predictus abbas Johannes hoc manerium tenet | The aforesaid Abbot John holds this manor. |
| Simo filius et heres predicte Agnetis est et etatis decem annorum est | Simon is the son and heir of the aforesaid Agnes and is [of] the age of ten years. |
A phrase that you will often see at the beginning of royal documents is
| Willelmus dei gratia rex | William by the grace of God king | gratia, -e (f.) grace |
| Maria dei gratia regina | Mary by the grace of God queen |
| ego Johannes dei gratia rex terram abbati Simoni hac carta do et confirmo | I, John, by the grace of God king, give and confirm the land by this charter to Abbot Simon |
Genitive plural ‘-ium’
Some third declension nouns end ‘-ium’ in the genitive plural.
For example pars, partis (f.) part; civis, civis (m.) citizen
| summa partium | the sum of the parts | summa, -e (f.) sum |
These and other irregular nouns are noted in our grammar resource and Latin word list.
Third declension adjectives
These have the same endings as third declension nouns except that adjectives have
- ‘-i’ for ablative singular
- ‘-ium’ for genitive plural
- ‘-ia’ for nominative, vocative and accusative neuter plural
There are two main forms of third declension adjectives.
1. Masculine and feminine are same; neuter is different.
Masculine and Feminine Neuter
| Case | Singular | Plural | Singular | Plural |
| Nominative | omnis | omnes | omne | omnia |
| Vocative | omnis | omnes | omne | omnia |
| Accusative | omnem | omnes | omne | omnia |
| Genitive | omnis | omnium | omnis | omnium |
| Dative | omni | omnibus | omni | omnibus |
| Ablative | omni | omnibus | omni | omnibus |
| communis , -e | common |
| fidelis, -e | faithful |
| finalis, -e | final |
| legalis, -e | lawful |
| parochialis , –e | parochial, parish |
| totalis, -e | total |
| summa totalis | sum total (used in accounts) |
| hec est finalis concordia | this is the final concord |
| lego terram ecclesie omnium sanctorum | I leave the land to the church of All Saints |
2. Masculine, feminine and neuter are the same in the nominative
These are declined in our grammar resource.
| ingens, ingentis | huge |
| presens, presentis | present |
| sapiens, sapientis | wise |
| vetus, veteris | old |
The nominative and genitive forms of these are given in our Latin word list.
They take the same endings as omnis.
| confirmamus hac presenti carta domine Mathildi ius curiam tenere |
We confirm by this present charter to the lady Matilda the right to hold a court. |
Did you notice the use of tenere to mean ‘to hold’?
Checklist
Are you confident with
- the genitive singular ending of third declension nouns?
- how to decline rex?
- which three endings are different in third declension adjectives and nouns?