I want to ask "what is their use ?"

So, I can write either {lo'chaj 'oH nuq'e'}, or I can write {nuq 'oH
lo'chaj'e'}.

Is there an actual difference between these two klingon sentences ?

None that we've been told. The nuq 'oH form occurs much more often than the 'oH nuq'e' form.

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SuStel
http://trimboli.name