3RD DECLENSION NOUNS that have the same number of syllables in the nominative as in the genitive, or that have a stem ending in two or more consonants take "-ium" in the plural genitive
3RD DECLENSION / MASCULINE & FEMININE I DECLENSION NOUNS with -ium in the genitive plural
Eg.: urbs, urbis
| case | Singular | Plural |
| Nom. | varies | -es |
| Gen. | -is | -ium |
| Dat. | -i | -ibus |
| Acc. | -em | -es |
| Abl. | -e or -i | -ibus |
| Voc. | same as nominative | -es |
3RD DECLENSION / NEUTER I DECLENSION NOUNS with -ium in the genitive plural
Eg.: mare, maris
| case | Singular | Plural |
| Nom. | varies, -is | -ia or -a |
| Gen. | -is | -ium |
| Dat. | -i | -ibus |
| Acc. | same as nominative | -ia or -a |
| Abl. | -i or -e | -ibus |
| Voc. | same as nominative | -ia or -a |
3RD DECLENSION / MASCULINE & FEMININE I DECLENSION NOUNS with -um in the genitive plural
Eg.: homo, hominis
| case | Singular | Plural |
| Nom. | varies | -es |
| Gen. | -is | -um |
| Dat. | -i | -ibus |
| Acc. | -em | -es |
| Abl. | -e or -i | -ibus |
| Voc. | same as nominative | -es |
3RD DECLENSION / NEUTER I DECLENSION NOUNS with -um in the genitive plural
Eg.: caput, capitis
| case | Singular | Plural |
| Nom. | varies, -is | -ia or -a |
| Gen. | -is | -um |
| Dat. | -i | -ibus |
| Acc. | same as nominative | -ia or -a |
| Abl. | -i or -e | -ibus |
| Voc. | same as nominative | -ia or -a |
