〜に違いない — JLPT N2 Grammar

Learn how to use 〜に違いない (ni chigainai) to express strong certainty and confident inference — 'must be; there's no doubt that; I'm sure that.' Includes structure, nuance, examples, and comparisons.

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Pattern

V-plain form + に違いない い-adj-plain + に違いない な-adj + に違いない (drop だ before に違いない) Noun + に違いない (drop だ before に違いない)

The clause before に違いない is the speaker's conclusion or inference. The pattern applies to all tenses: 〜したに違いない (must have done), 〜するに違いない (must do / will certainly).

Formality

Neutral. に違いない is used naturally across all registers — casual conversation, formal writing, news articles, and academic texts. It is one of the most common expressions of strong inference in Japanese.

Meaning

Must be ~; there's no doubt that ~; I'm certain that ~; definitely ~

〜に違いない expresses the speaker's strong, confident inference or conviction based on evidence, logic, or experience. The speaker is not guessing randomly — they are drawing a conclusion from what they observe or know, and expressing high certainty about it.

Explanation

に違いない is composed of に (particle) + 違い (ちがい, "difference; mistake; discrepancy") + ない (negative). The literal meaning is "there is no mistake about this" — i.e., the speaker is certain their conclusion is correct. This transparency makes the pattern easy to remember and understand.

The defining characteristic of に違いない is that it expresses the speaker's own strong conviction. It is NOT used to report external evidence objectively (for that, use 〜によると or 〜らしい), but rather to state the speaker's confident personal conclusion: 見て、彼は疲れているに違いない (Look — he must be tired, I'm sure of it).

に違いない is used across all tenses. In the past tense (〜たに違いない), it expresses confident inference about what happened: 彼は知っていたに違いない (He must have known). In the present/future, it expresses confident belief about a current or upcoming state: 彼女なら合格するに違いない (She will definitely pass, I'm sure of it).

Degree of certainty: に違いない expresses higher certainty than 〜はずだ (logical expectation based on rules or facts) and much higher certainty than 〜だろう (speculation/guess). The speaker using に違いない is not merely speculating — they are convinced.

Example Sentences

  1. あの笑顔を見れば、試験に合格したに違いない。 Ano egao wo mireba, shiken ni goukaku shita ni chigainai. Seeing that smile, he must have passed the exam.

  2. こんなに遅い時間に電話してくるなんて、何か急なことがあったに違いない。 Konna ni osoi jikan ni denwa shite kuru nante, nani ka kyuu na koto ga atta ni chigainai. Calling at such a late hour — something urgent must have happened.

  3. 彼女は毎日練習しているから、発表会できっと上手に演奏するに違いない。 Kanojo wa mainichi renshuu shite iru kara, happoukai de kitto jouzu ni ensou suru ni chigainai. Since she practices every day, she will definitely perform well at the recital.

  4. 財布がない。家に忘れてきたに違いない。 Saifu ga nai. Ie ni wasurete kita ni chigainai. My wallet is gone. I must have left it at home.

  5. あのレストランはいつも満席だ。料理がとてもおいしいに違いない。 Ano resutoran wa itsumo manseki da. Ryouri ga totemo oishii ni chigainai. That restaurant is always full. The food must be very good.

  6. 彼の態度から見て、すでに知っていたに違いない。 Kare no taido kara mite, sude ni shitte ita ni chigainai. Judging from his attitude, he must have already known.

Common Mistakes

Mistake 1: Using に違いない for guesses without evidence. に違いない implies confident inference based on something — evidence, logical reasoning, or observation. Using it for pure guesses or speculation makes it sound too strong or inappropriate. For guesses, use だろう or かもしれない.

  • Appropriate: 声が小さいし、震えている。彼は怖がっているに違いない。(Evidence → confident conclusion)
  • Inappropriate: 明日は雨かもしれないけど、晴れるに違いない。(Pure wishful guess — contradicts the confident certainty of に違いない)

Mistake 2: Attaching に違いない after な-adjective + だ or noun + だ. With な-adjectives and nouns, drop だ before に違いない.

  • Incorrect: ×元気だに違いない
  • Correct: 〇元気に違いない (must be fine/healthy)
  • Incorrect: ×先生だに違いない
  • Correct: 〇先生に違いない (must be a teacher)

Compare With

Pattern Meaning Key Difference
〜に違いない must be; I'm certain that Strong personal conviction. Speaker is highly confident based on evidence or reasoning.
〜はずだ should be; expected to be Logical expectation based on rules, facts, or established circumstances. More objective. Less personal conviction.
〜らしい seems like; apparently Based on external evidence or hearsay — reports information gathered from outside. More objective.
〜だろう / でしょう probably; I think ~ Speculation or inference with lower certainty. Speaker is making a guess, not a conviction.
〜かもしれない might; perhaps Low certainty. Speaker is acknowledging possibility, not expressing confidence.

Certainty scale (highest to lowest): に違いない > はずだ > だろう > らしい / ようだ > かもしれない

Key pair: に違いない vs. はずだ

  • に違いない: "I'm personally convinced" — speaker's strong conviction.
  • はずだ: "logically/objectively, this should be so" — based on external facts, rules, or schedules.

Example: 電車は8時に来るはずだ (The train should come at 8 — it's scheduled). vs. 彼はもう知っているに違いない (He must already know — I'm convinced of it from his behavior).