ei kusine · (female) cousin
Feminine (ei)
Indefinite singular
ei kusine
Definite singular
kusina
Indefinite plural
kusiner
Definite plural
kusinene
Feminine nouns (ei) can always be written with en as well: ei bok, boka or en bok, boken. Both are correct Bokmål.
How to guess the gender Nouns: gender and articles