〜じゃないか / 〜じゃない: Seeking Agreement & Realization (N4)
What it means
You already know じゃない as the casual negative — "is not" (see 〜じゃない as negation). But with a different tone, the very same word does the opposite job: it invites the listener to agree with you, or it voices a sudden realization or surprise. Think of English "isn't it?", "right?", or "see — it is!"
So いいじゃない can mean either "It's not good" (flat negation) or "That's good, isn't it!" (warm agreement). Spoken Japanese tells them apart by intonation; written Japanese leans on context and punctuation (often a ! or ？).
この店、おいしいじゃないか。
この みせ、おいしいじゃないか。
This place is delicious, isn't it!
Said with an upbeat, exclamatory tone — agreement, not negation.
ヤッタン、ちゃんとできるじゃない。
ヤッタン、ちゃんと できるじゃない。
Yattan, you can do it after all, can't you!
A pleased realization — 'turns out you can!'
ほら、言ったじゃない。
ほら、いったじゃない。
See? I told you, didn't I!
言ったじゃない = reminding the listener of something you already said.
How to form it
Attach じゃない (casual) or じゃないか to the plain form of verbs, い-adjectives, and nouns/な-adjectives. With nouns and な-adjectives, drop the だ first.
| Word type | Plain form | + じゃない(か) | Meaning |
|---|---|---|---|
| Verb | できる | できるじゃない(か) | "You can do it, can't you!" |
| Verb (past) | 言った | 言ったじゃない(か) | "I told you, didn't I!" |
| い-adjective | いい | いいじゃない(か) | "That's good, isn't it!" |
| な-adjective | 元気（だ） | 元気じゃない(か) | "You're full of energy, aren't you!" |
| Noun | 子ども（だ） | 子どもじゃない(か) | "He's just a kid, isn't he!" |
The か is optional and adds a slightly stronger, more masculine or rhetorical punch. じゃない alone is softer and very common in everyday speech. Note that the noun/な-adjective だ is dropped: 元気じゃないか (not 元気だじゃないか).
Seeking agreement — "right?"
The friendliest use is pulling the listener onto your side. You state something you think is obvious and expect a nod back.
新しいカフェ、いいじゃないか。今度行こう。
あたらしい カフェ、いいじゃないか。こんど いこう。
The new café looks nice, doesn't it! Let's go sometime.
モチの料理、けっこう上手じゃない。
モチの りょうり、けっこう じょうずじゃない。
Mochi's cooking is pretty good, isn't it!
上手 is a な-adjective, so だ is dropped.
This overlaps with 〜でしょう ("…right?"), but じゃない carries more warmth and a touch of "come on, you see it too."
Expressing realization or surprise
The same pattern voices a discovery — often something you didn't expect, now confirmed in front of you.
あれ、雨が降ってるじゃないか。
あれ、あめが ふってるじゃないか。
Oh — it's raining, isn't it!
A sudden noticing: the rain is news to the speaker.
ヤッタンの弟、もう漢字が読めるじゃない。
ヤッタンの おとうと、もう かんじが よめるじゃない。
Yattan's little brother can already read kanji — look at that!
Surprised, impressed realization.
Reminding: "I told you, didn't I!"
With a past-tense verb, じゃない(か) often means "(you remember) I already said this." It can sound gentle or mildly scolding depending on tone.
だから気をつけてって言ったじゃないか。
だから きを つけてって いったじゃないか。
That's why I told you to be careful, didn't I!
先生も大丈夫だって言ったじゃない。
せんせいも だいじょうぶだって いったじゃない。
The teacher said it'd be fine too, remember!
Polite and formal versions
In polite speech, use 〜じゃないですか or the slightly more formal 〜ではないですか:
これ、便利じゃないですか。
これ、べんりじゃないですか。
This is handy, isn't it!
便利 is a な-adjective; だ is dropped before じゃないですか.
昨日、約束したではないですか。
きのう、やくそくした ではないですか。
We made a promise yesterday, didn't we!
In writing or speeches you'll meet 〜ではないか, the formal cousin of じゃないか (じゃ is just a contraction of では). It reads as more literary or emphatic: すばらしいではないか ("Isn't it wonderful!").
Common mistakes
- Treating every じゃない as negation. Tone and context decide. おいしいじゃない can be "It's not tasty" or "It's tasty, isn't it!" — listen for the rising/exclamatory delivery.
- Leaving だ on nouns and な-adjectives. Drop it: 元気じゃない (✓), not 元気だじゃない (✗). The だ only survives in the formal 〜ではないか when quoting (…したではないか).
- Adding です in the wrong spot. The polite form is 〜じゃないですか, not 〜じゃないかです.
- Overusing the か with strangers. 〜じゃないか can sound blunt or confrontational. With people you're not close to, soften to plain 〜じゃないですか.
Quick recap
- 〜じゃない(か) on a plain-form word = seek agreement ("isn't it?") or show realization/surprise ("see!").
- Tone flips it from negation to confirmation — falling-then-rising or exclamatory.
- Drop だ after nouns and な-adjectives: 元気じゃないか.
- Past verb + じゃない(か) often = "I told you, didn't I!"
- Polite: 〜じゃないですか / 〜ではないですか; formal/written: 〜ではないか.
Your turn
Decide whether each じゃない means negation or confirmation, and pick the right form.
Start the 5-question drill →Take the full N4 〜じゃないか drill →
Frequently asked questions
How is confirmation じゃない different from negative じゃない?
They're the same word but opposite jobs. Negative じゃない ('is not') is flat: おいしいじゃない = 'it's not tasty.' Confirmation じゃない is said with a rising or exclamatory tone: おいしいじゃない！= 'it's tasty, isn't it!' Context and intonation decide.
What does the か add in じゃないか?
It strengthens the nuance — more rhetorical, emphatic, and a bit more masculine. じゃない alone is softer and very common in casual speech. Both seek agreement or express surprise.
Do I drop だ after nouns and な-adjectives?
Yes. Say 元気じゃないか, not 元気だじゃないか. The だ only appears in the formal quoting pattern …したではないか.
What's the polite version?
Use 〜じゃないですか or the more formal 〜ではないですか: 便利じゃないですか ('it's handy, isn't it!'). In writing you'll also see 〜ではないか.