De or het synodevergadering?

The correct Dutch article is:

de synodevergadering

Rule Words ending in -ing: almost always de. See the rule

How to use synodevergadering

the synodevergaderingde synodevergadering
this synodevergaderingdeze synodevergadering
that synodevergaderingdie synodevergadering
our synodevergaderingonze synodevergadering
your synodevergaderingjouw synodevergadering
every synodevergaderingelke synodevergadering
which synodevergadering?welke synodevergadering?
a big synodevergadering / the big synodevergaderingeen grote synodevergadering, de grote synodevergadering