De or het introversie?

The correct Dutch article is:

de introversie

Rule Words ending in -tie and -sie: almost always de. See the rule
Meaning (Dutch) (psychologie) aandacht die naar binnen gericht is

How to use introversie

the introversiede introversie
this introversiedeze introversie
that introversiedie introversie
our introversieonze introversie
your introversiejouw introversie
every introversieelke introversie
which introversie?welke introversie?
a big introversie / the big introversieeen grote introversie, de grote introversie

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