| SgM | SgF | SgN | PlM | PlF | PlN | |
| Nom | þunnr | þunn (rule) | þunnt (rule) | þunnir (rule) | þunnar (rule) | þunn (rule) |
| Acc | þunnan (rule) | þunna (rule) | þunnt (rule) | þunna (rule) | þunnar (rule) | þunn (rule) |
| Dat | þunnum (rule) | þunnri (rule) | þunnu (rule) | þunnum (rule) | þunnum (rule) | þunnum (rule) |
| Gen | þunns (rule) | þunnrar (rule) | þunns (rule) | þunnra (rule) | þunnra (rule) | þunnra (rule) |
| SgM | SgF | SgN | Pl | |
| Nom | þunni (rule) | þunna (rule) | þunna (rule) | þunnu (rule) |
| Acc | þunna (rule) | þunnu (rule) | þunna (rule) | þunnu (rule) |
| Dat | þunna (rule) | þunnu (rule) | þunna (rule) | þunnum (rule) |
| Gen | þunna (rule) | þunnu (rule) | þunna (rule) | þunnu (rule) |
| Degree | |
| Comp | þunnari (rule) |
| Sup | þunnastr (rule) |