[tlhIngan Hol] Why DaH is an adverb ?

Perhaps it will sound strange, but I can't understand why DaH is an adverb. tuch is a noun and pa'logh is noun; nem, ben, leS, waQ etc. are all nouns. I can't understand why DaH is an adverb. Not that I have a problem with it being an adverb, but I just can't understand why it needs to be different. ~ channgan qIj