Indefinite article

Comes before the noun as in English:
en bil 'a car'
ei frue 'a married woman'
et hus 'a house'
et eple 'an apple'

Indefinite (no article in the plural)

biler 'cars'
fruer 'married women'
hus 'houses'
epler 'apples'

Note that one-syllable neuter nouns have no ending in the plural, except:
steder 'places'

Definite article

Goes at the end!

bilen 'the car'
frua 'the married woman' Watch out - frua NOT fruei!
huset 'the house'

Use -ene for the (plural), all genders:

bilene 'the cars'
fruene 'the married women'
husene 'the houses'

Omission of terminal definite article after a concept

Det hvite hus 'the White House'

det hvite huset 'the white house' (any old)

Det røde hav 'the Red See'