in the PONS Dictionary
| Case | Singular | Plural |
|---|---|---|
| Nominative | serum | sera |
| Genitive | serī | serōrum |
| Dative | serō | serīs |
| Accusative | serum | sera |
| Ablative | serō | serīs |
| Case | Singular | Plural |
|---|---|---|
| Nominative | sērum | sēra |
| Genitive | sērī | sērōrum |
| Dative | sērō | sērīs |
| Accusative | sērum | sēra |
| Ablative | sērō | sērīs |