既然

既然 (jìrán) is a conjunction meaning 'since' or 'given that,' used to introduce a fact that is already known or accepted, from which a conclusion or decision follows. Crucially, 既然 marks a reason the listener already agrees with — it does not present new information the way English 'because' does. It typically opens the first clause and is answered by 就 (jiù), 那 (nà), or 那么 in the second: 既然你累了，就早点休息 (since you're tired, rest early).

Two things trip up English speakers: first, 既然 is about an accepted premise, so 因为 (yīnwèi, 'because') is the word for genuinely explaining a new cause; second, the paired 就 is almost obligatory — dropping it sounds incomplete. 既然 often carries a slightly persuasive or reasoning tone, as if saying 'well, given that this is true, then it makes sense to…'.