～に違いない (certainty)

• Reading: にちがいない
• Romaji: ni chigainai
• Formation: Verb plain form + に違いない / い-Adj + に違いない / な-Adj + に違いない / Noun + に違いない
• Kanji breakdown: 違 (ちが) — differ, mistake

Meaning

Expresses the speaker's strong conviction that something must be the case. The speaker is convinced there is no mistake in their judgement. It translates as 'must be,' 'no doubt,' or 'certainly.'

に違いない literally means 'there is no difference' or 'there is no mistake,' expressing the speaker's highest degree of subjective certainty. It follows the plain form of verbs and い-adjectives, while な-adjectives and nouns take に直接 or with だ. It is more assertive than だろう or はず — the speaker feels virtually certain. The polite form is に違いありません. Unlike はず, which is based on logical expectation, に違いない is based on the speaker's personal conviction and gut feeling, though evidence may support it. It appears frequently in written Japanese and detective-style reasoning.

Examples

1. あの音は雷に違いない。 That sound must be thunder.
2. 犯人は内部の人間に違いない。 The culprit must be someone from inside.
3. こんなに売れているのだから面白いに違いない。 It's selling this well, so it must be interesting.

Usage Guide

Context: spoken, written, everyday

Tone: assertive

Do Say

• この手紙を書いたのは彼に違いない。
• あの人はプロに違いありません。
• 昨日の地震は大きかったに違いない。

Don't Say

• たぶんあの人は犯人に違いない。(たぶん implies uncertainty, which conflicts with the strong certainty of に違いない) → あの人は犯人に違いない。
• 明日は晴れるに関わらない。(に違いない is the correct expression — に関わらない means 'regardless of') → 明日は晴れるに違いない。

Origin & History

に違いない combines the particle に, the noun 違い (difference/mistake), and ない (not exist), literally meaning 'there is no discrepancy.' It solidified as an expression of strong conviction in early modern Japanese.

Cultural Context

Generation: All ages

Social background: Universal