ei skjorte · shirt
Feminine (ei)
Indefinite singular
ei skjorte
Definite singular
skjorta
Indefinite plural
skjorter
Definite plural
skjortene
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