| Sg | Pl | |
| Nom | fjörðr | fjörðar (rule) |
| Acc | fjörð (rule) | fjörða (rule) |
| Dat | firði (rule) | fjörðum (rule) |
| Gen | fjörðs (rule) | fjörða (rule) |
| Sg | Pl | |
| Nom | fjörðrinn (rule) | fjörðarnir (rule) |
| Acc | fjörðinn (rule) | fjörðana (rule) |
| Dat | firðinum (rule) | fjörðunum (rule) |
| Gen | fjörðsins (rule) | fjörðanna (rule) |