While I understand that it’s common in English and perhaps other human languages to answer a “Why?” question with a dependent clause starting with “Because”, I’m curious as to whether or not we can assume the same is true in Klingon.

Likely, this is less of a grammar question than a cultural one, since it’s obvious that you CAN do it. The question is more whether a native Klingon speaker (in the imaginary world where they exist) would receive such an answer with aplomb, or whether it would raise eyebrows and sideways glances, like walking up to someone working at a desk, putting out your hand for a handshake, yelling, {nuqneH!}

One complete sentence version would be:

{ja’chuqtaHvIS loDqoqpu’, jatlhlaHba’ *SIparta’ngan* be’.}

And no, I don’t expect anyone to agree with me.

I think you're speculating on whether Klingons would utter a subordinate clause without using a main clause... and the answer is yes.

qIrq vIjeylaHchugh... If I could defeat Kirk... (Captain Klaa, Star Trek V)
lIchopbe'chugh ghewmey If the bugs do not bite you. (Power Klingon) (This one is even the direct answer to a question.)

And in the general case, we see instances where answers are shortened. Conversational Klingon tells us we can shorten complete answers to just HIja' or ghobe'. We see people reading status reports in heading-content format like jabbI'ID pItlh. We see questions posed as statements, like vaj Daleghpu'. We see nouns used as commands, like chuyDaH and HaSta. We have noun exclamations, like Qapla' and Ha'DIbaH. We have sentences without verbs or pronouns, like DIvI' neHmaH and DoS jonta' neH. We get explanations without main verbs, like bach Do', qaH. We have nouns as questions, like latlh? To which the the answer is more nouns: wa' tera'ngan je wa' romuluSngan.

So we have lots and lots of reason to believe that Klingons use incomplete sentences when speaking to each other. We also know it's not impossible for Klingons to utter subordinate clauses without main clauses, and to use these clauses as answers to questions. We have far more examples of "formal" writing than we do of Klingons speaking to each other in normal language. I see no reason at all to restrict oneself to answering questions with full sentences, and I see no reason to single out -mo' in this regard.

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SuStel
http://trimboli.name