Nominative singulars and bases
The third declension consists of Latin words with stems ending in a consonant or ·i. This declension is the most difficult, because for each of its nouns you must learn two forms:
- an irregular nominative singular form
- a base, to which endings are added.
In vocabulary lists, nouns are listed by their nominative singular form and their genitive singular form. You must learn both of these. To work out the noun's base, remove the ·is ending from the genitive singular.
| vocab entry | irregular nominative singular | base |
|---|---|---|
| comes comitis c. | comes | comit· |
| litus litoris n. | litus | litor· |
| navis navis f. | navis | nav· |
Non-neuter nouns
Non-neuter third declension nouns decline like this:
In the next two tables, the forms containing dots (·) are based on the base of the word.
| singular | plural | |
|---|---|---|
| nominative | comes | comit·es |
| vocative | comes | comit·es |
| accusative | comit·em | comit·es |
| genitive | comit·is | comit·um |
| dative | comit·i | comit·ibus |
| ablative | comit·e | comit·ibus |
Neuter nouns
Neuter third declension nouns decline like this:
| singular | plural | |
|---|---|---|
| nominative | litus | litor·a |
| vocative | litus | litor·a |
| accusative | litus | litor·a |
| genitive | litor·is | litor·um |
| dative | litor·i | litor·ibus |
| ablative | litor·e | litor·ibus |
Exceptions
Genitive plurals ending in ·ium
Some third-declension nouns have a genitive plural in ·ium. Here are all the third-declension nouns from the first year course whose genitive plural ends in ·ium:
| word | genitive plural | meaning |
|---|---|---|
| civis civis c. | civium | citizen |
| collis collis m. | collium | hill |
| hostis hostis c. | hostium | enemy, enemy soldier |
| mare maris n. | marium | sea |
| moenia moenium n. pl. | moenium | city walls |
| mons montis m. | montium | mountain, hill |
| mors mortis f. | mortium | death |
| navis navis f. | navium | ship |
| nox noctis f. | noctium | night |
| urbs urbis f. | urbium | city |
Neuter stems ending in ·i
Neuter nouns whose nominative singular ends in ·e have stems ending in ·i. These words are have a special ablative singular ending, ·i.
The only noun like this in the first year course is mare maris n., sea.
| singular | plural | |
|---|---|---|
| nominative | mare | maria |
| vocative | mare | maria |
| accusative | mare | maria |
| genitive | maris | marium |
| dative | mari | maribus |
| ablative | mari | maribus |