ei bukse · trousers
Feminine (ei)
Indefinite singular
ei bukse
Definite singular
buksa
Indefinite plural
bukser
Definite plural
buksene
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