〜じゃないか / 〜じゃない: Seeking Agreement & Realization (N4)
When じゃない stops meaning "not"
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 ？). The trap for learners is reading every じゃない as negation — let the rising, exclamatory delivery, and the "see?/right?" test, decide.
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.
Building it onto a plain clause
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 — say 元気じゃない (✓), never 元気だじゃない (✗).
| 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. Because it clamps onto a whole plain clause — including past verbs — the confirming reading stays clearly apart from a flat negative one.
Pulling the listener onto your side
The friendliest use is seeking agreement: 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."
Noticing out loud — and reminding
The same pattern voices a discovery — often something you didn't expect, now confirmed right 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.
Swap in a past-tense verb and じゃない(か) shifts to "(you remember) I already said this." Depending on tone it lands as gentle nudge or mild scolding.
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!
Casual, polite, and written registers
In polite speech, use 〜じゃないですか or the slightly more formal 〜ではないですか. Mind the word order: the polite marker is 〜じゃないですか, never 〜じゃないかです.
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!"). One caution with the bare か: to people you're not close to it can sound blunt or confrontational, so soften to plain 〜じゃないですか outside familiar company.
The short version
- 〜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.
Practice it
Decide whether each じゃない means negation or confirmation, and pick the right form.
＿＿＿に入れるのに最もよいものを選びなさい。
Choose the grammar pattern that best completes the sentence.
これ、君の本＿＿＿。
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.
Where 〜じゃないか / 〜じゃない fits
Shaky on this? Get these solid first
- か Particle · N5 — The particle か turns a statement into a question (〜ですか), means 'or' between nouns (AかB), and makes question words indefinite: だれか someone, なにか something, どこか somewhere.
Don't confuse it with
- 〜でしょう / 〜だろう · N5 — でしょう means 'probably' and, with a rising tone, 'right?'. Learn how it attaches to verbs, adjectives, and nouns, its casual form だろう, and why forecasts love it.
Once this clicks, go on to
- 〜と思う · N5 — 〜と思う lets you say what you think: [plain form] + と思う. Learn the quotative と, why the clause stays plain, the 〜ようと思う 'I'm thinking of doing' use, and 〜と思っている.
More N4 grammar to explore
Keep going with related patterns at the same level:
- 〜かどうか — 〜かどうか packs a yes/no question inside a bigger sentence: 来るかどうか分からない ('I don't know whether he'll come'). Learn the formation, noun and な-adjective rules, and how it differs from question-word + か.
- かな・かしら・かい — かな means 'I wonder' (to yourself), かしら is its softer, traditionally feminine twin, and かい is a friendly casual yes/no question. Learn the nuances, register, and 〜ないかな ('I hope…').
- 〜方 — Add 方 (かた) to a verb's ます-stem to make a noun meaning 'how to do' or 'the way of doing': 作り方 (how to make), 使い方 (how to use), 読み方 (reading).
- 〜ことになる — 〜ことになる means a decision was made by circumstances or others: 転勤することになった. Learn the formation, the modest 'it turns out' nuance, and 〜ことになっている for rules.
- 〜ことにする — 〜ことにする expresses a decision you make by your own will: 毎日運動することにした ('I've decided to exercise every day'). Learn the formation, the negative, and the habit form ことにしている.
- 急に — 急に means 'suddenly' or 'abruptly' and works as an adverb before a verb: 急に雨が降ってきた. Learn 急に vs 急な (adjective) and how it differs from 突然.