De or het demologie?

The correct Dutch article is:

de demologie

Rule Words ending in -logie: always de. See the rule
Meaning (Dutch) wetenschap die de samenstelling van de bevolking bestudeert

How to use demologie

the demologiede demologie
this demologiedeze demologie
that demologiedie demologie
our demologieonze demologie
your demologiejouw demologie
every demologieelke demologie
which demologie?welke demologie?
a big demologie / the big demologieeen grote demologie, de grote demologie

Meaning, plural, diminutive, pronunciation and translations: WikiWoordenboek (Dutch Wiktionary) (CC BY-SA 4.0). Example sentences: Tatoeba (CC BY 2.0 FR).