De or het railruwheid?

The correct Dutch article is:

de railruwheid

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

How to use railruwheid

the railruwheidde railruwheid
this railruwheiddeze railruwheid
that railruwheiddie railruwheid
our railruwheidonze railruwheid
your railruwheidjouw railruwheid
every railruwheidelke railruwheid
which railruwheid?welke railruwheid?
a big railruwheid / the big railruwheideen grote railruwheid, de grote railruwheid