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JLPT N4Expressions

じゃないか— Isn't it? / Come on! (casual)

The casual version of ではないか. Expresses rhetorical questions, realization, mild surprise, or a bid for agreement; can also carry light accusation or enthusiasm.

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Pro lessonUNIT 21 · EXPRESSIONS

Structure · 形

[Plain form] + じゃないか

Examples · 例文

  • もう12時じゃないか！急ごう。

    Mō jūniji ja nai ka! Isogō.

    It's already 12! Let's hurry.

    Surprised realization + call to action

  • そのアイデア、いいじゃないか。

    Sono aidea, ii ja nai ka.

    That idea's great, isn't it!

    Positive affirmation / approval

  • あれ、山田さんじゃないか！

    Are, Yamada-san ja nai ka!

    Oh, isn't that Yamada-san!

    Surprised recognition of a person

Usage notes · 注意

  • Key Concept: じゃないか = casual;
  • Note: ではないか = formal.
  • Detail: falling intonation = rhetorical assertion;
  • Detail: rising intonation = genuine question.
  • Polite version: じゃないですか.
  • In formal writing: ではないでしょうか.
  • Summary: common among male speakers but widely understood by all.

Commonly confused with

The JLPT rarely asks whether you recognise a pattern — it asks which of several similar patterns fits. These are the ones じゃないか is tested against.

vsではないか (formal)

Same meaning, register difference: じゃないか is spoken/casual (and often masculine), ではないか is formal/literary.

vsじゃない (isn't/negation)

Plain じゃない is simple negation ('is not') or a tag question. Adding か turns it into an emphatic rhetorical exclamation of surprise or realization.

More expressions

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