1A conversational conjunction — the colloquial form of では — used to change topic, draw a conclusion, make a suggestion, or wrap up a conversation (e.g., 'well then,' 'so').
じゃあ、明日また会おう。
Well then, let's meet again tomorrow.
もう時間だね。じゃあ、失礼します。
It's time already. Well then, I'll be excusing myself.
じゃあ、それで決まりだね。
So that's decided, then.
じゃあ、次の話題に移りましょう。
Well then, let's move on to the next topic.