2ND DECLENSION / MASCULINE O DECLENSION NOUNS with no "e"
Eg.: amicus
| case | Singular | Plural |
| Nom. | -us | -i |
| Gen. | -i | -orum |
| Dat. | -o | -is |
| Acc. | -um | -os |
| Abl. | -o | -is |
| Voc. | -e | -i |
2ND DECLENSION / MASCULINE O DECLENSION NOUNS that keep the "e"
Eg.: puer
| case | Singular | Plural |
| Nom. | puer | pueri |
| Gen. | pueri | puerorum |
| Dat. | puero | pueris |
| Acc. | puerum | pueros |
| Abl. | puero | pueris |
| Voc. | puer | pueri |
2ND DECLENSION / MASCULINE O DECLENSION NOUNS that drop the "e"
Eg.: ager
| case | Singular | Plural |
| Nom. | ager | agri |
| Gen. | agri | agrorum |
| Dat. | agro | agris |
| Acc. | agrum | agros |
| Abl. | agro | agris |
| Voc. | ager | agri |
2ND DECLENSION / NEUTER O DECLENSION NOUNS
Eg.: bellum, proelium
| case | Singular | Plural |
| Nom. | -um | -a |
| Gen. | -i/-* | -orum |
| Dat. | -o | -is |
| Acc. | -um | -a |
| Abl. | -o | -is |
| Voc. | -um | -a |
*Note: neuter o declension nous with "i" in the stem can drop one "i" in the genitive singular.
