The indefinite article (corresponding to English ‘a(n)’) is, in Danish, either
EN (common gender) or ET (neuter).

The definite (or end) article (corresponding to English ‘the’) is -(E)N or -(E)T in the singular and -(E)NE in the
plural. The term ‘end article’ refers to the fact that it is added to the end
of the noun, either to its dictionary form or (in the plural) to its inflected
form:

1) SINGULAR
a) Indefinite (en/et)
en mand (a man)
en kvinde (a woman)
et hus (a house)
et æble (an apple)

b) Definite (End article) (-(e)n/-(e)t)
manden (the man)
kvinden (the woman)
huset (the house)
æblet (the apple)

2) PLURAL (both genders) (-(e)ne)
(e)r-plural
aviser (newspapers) – aviserne (the newspapers)
æbler (apples) – æblerne (the apples)

e-plural
borde (tables) – bordene (the tables)
heste (horses) – hestene (the horses)

zero-plural
mænd (men) – mændene (the men)
sko (shoes) – skoene (the shoes)

Reference: Danish an Essencial Grammar (Tom Lundskær-Nielsen and Philip Holmes), 2ed.