Why is it das Apartment?

Apartment ends in -ment, and nouns ending in -ment are neuter: in a German dictionary, 97% of them take das.

All nouns ending in -ment
Sense 1
das

Meaning

[1] small comfortable apartment

[1] kleine komfortable Wohnung

Examples

[1] Some rent an apartment at their place of work as a second home.

[1] Manche mieten ein Apartment an ihrem Arbeitsort als Zweitwohnung.

[1] “There were three framed photos on one wall of her apartment in Ogba” [2]

[1] „An einer Wand ihres Apartments in Ogba hingen drei eingerahmte Fotos.“[2]
More source examples (1)

These dictionary examples can include historical and less common uses.

[1] "I gradually had to get rid of this apartment." [3]

[1] „Dieses Apartment mußte ich allmählich loswerden.“[3]

Declension

1 Singular Plural
Nominativ das Apartment die Apartments
Genitiv des Apartments der Apartments
Dativ dem Apartment den Apartments
Akkusativ das Apartment die Apartments

Pronunciation

Dictionary entries include material from Wiktionary. Wiktionary