tasasen is the singular genitive of tasanen.

tasanenA

Norwegian Bokmål

slettA; jevnA

Kven – Norwegian Bokmåldict-fkv-nob/src/A_fkvnob.xml:1447Edit on GitHub Suggest

Case	Sg	Pl
Nom	tasanen	tasaset
Gen	tasasen	tasasten
Par	tasasta	tasasia / tasassiita / tasassii
Ill	tasasheen	tasashiin
Ine	tasasessa	tasasissa
Ela	tasasesta	tasasista
Ade	tasasella	tasasilla
Abl	tasaselta	tasasilta
All	tasasellet / tasaselle	tasasillet / tasasille
Abe	tasasetta	tasasitta
Ess	tasasenna	tasasinna
Tra	tasaseksi	tasasiksi
Com		tasasinne