N5 — outside your level filter

じゃあ

じゃあjaaN5casual

well then; in that case — takes it as settled and moves on

「今日きょうはちょっと無理むりなんだ。」「じゃあ、明日あしたの夕方ゆうがたは？」

"kyou wa chotto muri nan da." "jaa, ashita no yuugata wa?"

"I can't make it today." "Well then, how about tomorrow evening?" casual

じゃ、また来週らいしゅうね。

ja, mata raishuu ne.

Right, see you next week. casual

All examples4

well then; in that case — offers a next step after they spoke

「今日きょうはちょっと無理むりなんだ。」「じゃあ、明日あしたの夕方ゆうがたは？」
"kyou wa chotto muri nan da." "jaa, ashita no yuugata wa?"
"I can't make it today." "Well then, how about tomorrow evening?" casual
資料しりょうは全員ぜんいんに行いき渡わたったようですね。では、本日ほんじつの議題ぎだいに入はいります。
shiryou wa zen'in ni ikiwatatta you desu ne. dewa, honjitsu no gidai ni hairimasu.
It looks like everyone has the handouts. In that case, I'll get started on today's agenda. neutral
それでは、ただいまより開会かいかいの辞じを申もうし上あげます。
soredewa, tadaima yori kaikai no ji o moushiagemasu.
With that, I will now deliver the opening address. formal

well then — ends the talk so both people can go

じゃjacontraction
the short form, quicker and more casual. You'll hear it in a goodbye like じゃ、また。
ではdehaformal
the full, formal form behind じゃあ. You'll hear it in meetings and writing, like では、始はじめます。
それではsoredehaformal
an even fuller, more careful version of では. You'll hear it marking a new stage in ceremonies and formal events.

では can be ではない after a noun (学生がくせいではない), or で plus は
mid-sentence (ここでは静しずかに). じゃあ is neither, and only stands where
a new sentence could start.