| Singular | Plural | |
|---|---|---|
| Nominativ | lethargus, lethargus | lethargi, lethargi |
| Genitiv | lethargi, lethargi | lethargorum, lethargorum, lethargum, lethargum |
| Dativ | lethargo, lethargo | lethargis, lethargis |
| Akkusativ | lethargom, lethargom, lethargum, lethargum | lethargos, lethargos |
| Ablativ | lethargo, lethargo | lethargis, lethargis |
| Vokativ | letharge, letharge | lethargi, lethargi |