De or het expertkennis?

The correct Dutch article is:

de expertkennis

Rule Words ending in -nis: usually de. See the rule

How to use expertkennis

the expertkennisde expertkennis
this expertkennisdeze expertkennis
that expertkennisdie expertkennis
our expertkennisonze expertkennis
your expertkennisjouw expertkennis
every expertkenniselke expertkennis
which expertkennis?welke expertkennis?
a big expertkennis / the big expertkenniseen grote expertkennis, de grote expertkennis