De or het parterreappartement?

The correct Dutch article is:

het parterreappartement

Rule Words ending in -ment: usually het. See the rule

How to use parterreappartement

the parterreappartementhet parterreappartement
this parterreappartementdit parterreappartement
that parterreappartementdat parterreappartement
our parterreappartementons parterreappartement
your parterreappartementjouw parterreappartement
every parterreappartementelk parterreappartement
which parterreappartement?welk parterreappartement?
a big parterreappartement / the big parterreappartementeen groot parterreappartement, het grote parterreappartement