“〜jan・〜ja nai”: Isn't It? / I Knew It! (colloquial confirmation) [JLPT N4]
Content by NTJ Kuma · Nihongo to Japan editorial team · Updated July 27, 2026
「面白いじゃん！」「山田さんじゃない？」 — casual “nice, huh!” vs “isn't that …?”
「できるじゃん！」 — super-casual “isn't it／…, right?”
Your friend pulls it off and you clap: 「できるじゃん！」 (you can do it after all!) — 「じゃん」 is a super-casual tone of confirmation/discovery, a contraction of 「じゃない（か）」, carrying “…, right／isn't it／just as I thought.” 「じゃん／じゃない」 are used to confirm with the listener, or express discovery/surprise. This guide teaches this everyday young-people's colloquialism and flags where formality draws the line.
じゃん／じゃない: colloquial confirmation
- 〜じゃん = “…, right／isn't it” (contraction of じゃない, super-casual): 面白いじゃん (it's fun, right); できるじゃん (you can do it after all — praise/discovery).
- 〜じゃない（か） = “isn't it ~?” (confirmation, rhetorical, surprise): 山田さんじゃない？ (isn't that Mr. Yamada?).
Common thread: confirming with the listener, or an “I've realized” tone.
How to Connect
| Form | Nuance | Example |
|---|---|---|
| plain form ＋ じゃん | …, right／isn't it (super-casual) | 面白いじゃん |
| noun／na-adj ＋ じゃん | …, right | 便利じゃん |
| 〜じゃない（か） | isn't it ~? (confirm, surprise) | 山田さんじゃない？ （Isn't that Yamada?） |
See it in context
- この映画、すごく面白いじゃん！(This movie's really good, right!) — discovery, praise
- あれ、山田さんじゃない？(Hey, isn't that Yamada?) — confirmation, surprise
- やっぱりそうじゃん！(Just as I thought!) — as expected
- できるじゃん！すごいね。(You can do it! Impressive.) — praise
- それ、私の傘じゃない？(Isn't that my umbrella?) — confirmation
⚠️ Where learners slip up
① 「じゃん」 is super-casual — never use it formally. In interviews, business, or with seniors, 「じゃん」 is rude. It's for friends and peers. Formally, use 「〜ではないですか／〜ですよね」.
② 「じゃない」's intonation sets the meaning. Rising 「山田さんじゃない↗？」 = confirmation (isn't it Yamada?); falling 「行くじゃない↘」 = assertion (of course we're going). Judge by intonation.
③ 「じゃん」 leans eastern Japan／young people. Common in Kanto and younger generations; Kansai has 「やん」 (ええやん = いいじゃん). Region and generation vary.
🔄 Nuance & comparison: じゃん／じゃない／でしょ／よね
| Form | Nuance | Setting |
|---|---|---|
| 〜じゃん | …, right／isn't it (super-casual) | friends, casual |
| 〜じゃない（か） | isn't it ~? (confirm, surprise) | colloquial |
| 〜でしょ（う） | …, right? (confirm, guess) | general colloquial |
| 〜よね | …, right? (seeking agreement) | general, politer |
💡 The key point in use
「じゃん」 is a young-people's catchphrase, and using it makes you sound “local” — 「できるじゃん！」 when a friend succeeds, 「いいじゃん！」 when you like something, both very natural. But remember: it's super-casual — never in formal settings (interviews, business, with seniors), where it's quite rude. To confirm formally, use 「〜ですよね／〜ではないでしょうか」. Let loose with friends, put it away for anything outward-facing.
❓ FAQ
Q: What is 「じゃん」 a contraction of?
Of 「じゃない（か）」 (じゃないか → じゃん). So 「面白いじゃん」 ≒ 「面白いじゃないか」 = it's fun, right／isn't it fun. It compresses the confirmation/discovery tone into one super-casual 「じゃん」, an everyday colloquialism of Kanto and younger generations.
Q: Can I use 「じゃん」 with a boss or senior?
Absolutely not. 「じゃん」 is extremely casual, and using it with a boss, senior, or client is very rude. In formal or polite settings, use 「〜ですよね」「〜ではないですか」. Save 「じゃん」 for friends, peers, family, and other close people.
🖊️ Practice Questions (5)
Q1. 「この映画、面白い___！見てよかった。」(This movie is pretty good! — pleasant surprise / sharing)
(A) じゃない？ (B) じゃん (C) ね (D) よ
Q2. 「あれ、山田さん___？」(Isn't that Yamada? — confirming recognition)
(A) じゃん (B) じゃない (C) だ (D) ね
Q3. 「じゃん」is a contraction of what?
(A) じゃないか
(B) じゃないで
(C) じゃない (completely different)
(D) じゃあない
Q4. 口語で「やっぱりそう___？」(So it really is that way, isn't it? — seeking agreement)
(A) じゃん (B) じゃない (C) ね (D) よ
(A) Can't do it, huh
(B) You really can do it! (surprise / positive appraisal)
(C) Can't you do it?
(D) Did you do it?
Answer Explanations
1. (B) じゃん ── 「この映画、面白いじゃん！」(This movie is pretty good!) = the speaker's own surprise/discovery, actively sharing a positive assessment. じゃない (A) seeks confirmation (「面白いじゃない？」), a different nuance.
2. (B) じゃない ── 「あれ、山田さんじゃない？」(Isn't that Yamada?) with rising intonation = confirming identity and seeking the other's agreement. (A) じゃん leans toward a 'discovery/surprised assertion' (山田さんじゃん！); this question is about 'seeking confirmation,' so じゃない？ is used; (C) だ / (D) ね lack this confirming tone.
3. (A) じゃないか ── 「じゃん」is a contraction of 「じゃないか」; its original meaning is 'isn't it?', but after contraction the nuance becomes 'discovery/surprise/sharing' rather than a purely negative question.
4. (B) じゃない ── 「やっぱりそうじゃない？」(So it really is that way, isn't it?) = confirming / seeking agreement; じゃない with rising intonation = confirmation.
5. (B) ── 「できるじゃん！」(You really can do it!) = positive surprise/praise, similar to 'I told you you could do it!' Here じゃん shows the speaker's pleasant surprise and recognition of the other's ability.