De or het triosynode?

The correct Dutch article is:

de triosynode

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

How to use triosynode

the triosynodede triosynode
this triosynodedeze triosynode
that triosynodedie triosynode
our triosynodeonze triosynode
your triosynodejouw triosynode
every triosynodeelke triosynode
which triosynode?welke triosynode?
a big triosynode / the big triosynodeeen grote triosynode, de grote triosynode