expression
Casual tag question seeking agreement or confirmation, similar to 'isn't it?' or 'right?'. Often used with a falling intonation when the speaker expects agreement.
これ、美味しいじゃないか。
This is delicious, isn't it?
あの人、田中さんじゃないか。
That person is Tanaka-san, isn't it?
expression
let's ...; why don't we ...; how about we ...; shouldn't we ...
Follows the volitional form of a verb to make a casual suggestion or invitation. Equivalent to 'let's do' or 'why don't we do'. The speaker is proposing an action involving the listener.
そろそろ行こうじゃないか。
Let's get going, shall we?
一緒に食べようじゃないか。
Why don't we eat together?