* Nominative forms of third declension nouns are highly variable; there is no one set or common ending.
Third Declension Masculine/Feminine i-stem
urbs, urbis, f. - city
Case
Singular
Plural
Nominative
urbs*
urb-ēs
Genitive
urb-is
urb-ium**
Dative
urb-ī
urb-ibus
Accusative
urb-em
urb-ēs
Ablative
urb-e
urb-ibus
* Nominative forms of third declension nouns are highly variable; there is no one set or common ending. ** Note the extra i in the genitive plural ending: -ium, rather than simply -um.
Third Declension Neuter
nōmen, nōminis, n. - name
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
* Nominative forms of third declension nouns are highly variable; there is no one set or common ending. ** The accusative forms of all neuter nouns, adjectives, and pronouns exactly match their nominative counterparts within the same number (e.g., neuter accusative singular = neuter nominative singular).
Third Declension Neuter i-stem
mare, maris, n. - sea
Case
Singular
Plural
Nominative
mare*
mar-ia***
Genitive
mar-is
mar-ium***
Dative
mar-ī
mar-ibus
Accusative
mare**
mar-ia***
Ablative
mar-ī***
mar-ibus
* Nominative forms of third declension nouns are highly variable; there is no one set or common ending. ** The accusative forms of all neuter nouns, adjectives, and pronouns exactly match their nominative counterparts within the same number (e.g., neuter accusative singular = neuter nominative singular). *** Note the replacement of the normal ablative singlar ending -e with -ī and the extra i in the endings of the nominative, genitive, and accusative plurals.