Sorry for being "off topic", but I have a Latin question one of you fine, learned fellows might be able to help me with. How could I best say "off topic" in Latin? Nagating agumentum, perhaps? Or would propositio be better fitting? What would the correct negation be?
There's no direct, universal translation for "off topic" in Latin -- or in many other languages either! You have to work the meaning into the particular sentence you are trying to say, but just how depends heavily on the sentence. What are you trying to say?
I would use for topic "res" - as in Lucretius' great work of natural philosophy De rerum natura
So for "off topic", I would go for "ab re" (for "from the matter/subject/topic", I think I remember my 5th declension nouns) followed by a verb.
I think "divergere" from which we get "diverge" and "divergence", to stray from, is the closest.
So using a participle, I'd say "ab re divergens" for "diverging from the topic". Of course you could always use "ab re divergo" for "I'm going off-topic" or "ab re diverges" for "you're going off-topic" (for 2nd person singular)
the adjective/adverb "off topic" is not really compatible with the structure of Latin.
An off-topic remark, statement or text in English is a digression (at least since Swift's Tale of a Tub with its Digression in Praise of Digressions), which is derived from the Latin 'digressio', meaning the same.
If I am going off-topic, I digress - and that's in Latin 'digredior'. If I went off-topic, 'digressus sum' in Latin.