N4
じゃないか
Isn't it?, Is it not?
キヨコはもうすぐ来るんじゃないか。
Isn't Kiyoko coming soon?
Explanation
「じゃないか」 has 2 uses
1Isn't it …?
With rising tone: checking, reminding or blaming: 「九時までに帰ってくるって言ったじゃないか」 didn't you say you'd be back by nine?
そのことじゃなかったか。
It was about that, wasn't it?
キヨコはもうすぐ来るんじゃないか。
Isn't Kiyoko coming soon?
2Well, look at that
With falling tone: surprise at noticing something: 「あれ、田中さんじゃないか」 hey, it's Tanaka!
この着物は綺麗じゃないか。
This kimono is beautiful, isn't it?
あなたの車は私の車より速いじゃないか。
Your car is faster than my car, isn't it?
Mixed up with
Rising shows doubt or displeasure: 「約束が違うじゃないか↗」 (That's not what we agreed!). Falling shows surprise or pleasure: 「いい味じゃないか↘」 (Hey, this tastes good).
This is a very casual, close-friends style and can sound scolding. Do not use it with elders, bosses or clients. To confirm or guess, use 「~ではありませんか」 or 「~のではないでしょうか」.