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JLPT N3 · Guessing & hearsay

に違（ちが）いない (ni chigai nai)

～に違いない — must be ～ / no doubt

In short · Expresses the speaker’s strong conviction, based on some grounds, that something is so: “it must be ～, there is no doubt.” It is for a judgment, not for something directly seen, and is common in writing and serious speech.
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Pattern

  • 動詞・イ形容詞 普通形＋に違いない plain form + に違いない (何かあったに違いない)
  • ナ形容詞語幹・名詞＋に違いない na-adjective stem or noun + に違いない (留守に違いない)

Meaning and connection

Verbs and i-adjectives take the plain form; na-adjectives and nouns take the bare stem with no だ or な. 違いない means “there is no mistake,” expressing the speaker’s strong certainty that leaves no room for doubt.

Compared with similar forms

It is stronger than 〜だろう or 〜かもしれない and close to 〜はずだ or 〜に決まっている. The grounds are the speaker’s own reasoning, so it may turn out wrong, and it is more subjective than 〜らしい. Do not use it for your own actions or facts you can plainly see.

Examples

  • あの人（ひと）は犯人（はんにん）に違（ちが）いない。

    Ano hito wa hannin ni chigai nai.

    That person must be the culprit.

    Noun + に違いない (no だ).

  • 電気（でんき）が消（き）えているから、留守（るす）に違（ちが）いない。

    Denki ga kiete iru kara, rusu ni chigai nai.

    The lights are off, so they must be out.

    The reason (lights off) supports the conclusion.

  • こんなに人（ひと）が集（あつ）まるとは、何（なに）かあったに違（ちが）いない。

    Konna ni hito ga atsumaru to wa, nani ka atta ni chigai nai.

    For this many people to gather, something must have happened.

    Past plain form (あった) + に違いない.

Common mistakes

  • Do not add だ or な before it: × 静かだに違いない, ○ 静かに違いない.
  • The polite form is 〜に違いありません. Do not use it for your own actions or plainly visible facts.

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