니

since / and then I found; also a casual question

Joining two clauses, it says the first one led to the second — either as a reason (역사가 있는 회사이니 'since it's a company with that much history') or as a discovery: 알고 보니 'as it turns out', 하다 보니 'as I kept doing it, it just became second nature'. The 보니 pattern is the one you'll hear most, and it always introduces something the speaker only realized afterwards. Separately, 니 also ends a casual question to someone close — 먹는 사람이 있니? 'is there anyone who eats it that way?' — which sounds motherly or a little old-fashioned.

Register: connective use neutral; question use casual and slightly old-fashioned