| Sg | Pl | |
| Nom | heiðr | heiðar (rule) |
| Acc | heiði (rule) | heiðar (rule) |
| Dat | heiði (rule) | heiðum (rule) |
| Gen | heiðar (rule) | heiða (rule) |
| Sg | Pl | |
| Nom | heiðrin (rule) | heiðarnar (rule) |
| Acc | heiðina (rule) | heiðarnar (rule) |
| Dat | heiðinni (rule) | heiðunum (rule) |
| Gen | heiðarinnar (rule) | heiðanna (rule) |