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.
This is delicious, isn't it?
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.
Let's get going, shall we?
That person is Tanaka-san, isn't it?
一緒に食べようじゃないか。
Why don't we eat together?
だろう is a more neutral tag question expressing likelihood, while じゃないか is casual and pushes the listener to agree.
じゃん is an even more colloquial, youth-slang variant of じゃないか used for the same confirming tag-question function.
じゃないか is the casual, contracted form used in informal speech, while ではないか is the fuller, slightly more formal or literary form of the same tag-question/suggestion expression.
じゃないか is the standard Japanese equivalent used nationwide for confirmation or rhetorical emphasis, while ちゃうか carries a distinctly Kansai-ben flavor.
ではないか is the formal or written counterpart of じゃないか, used in polite speech or formal writing where じゃないか would be too casual.
Contraction of ではないか (de wa nai ka), a negative question form meaning 'is it not?'. The casual contraction じゃ (ja) replaces では (de wa).