GRAMMAR DETAIL

に違いない

must be · without a doubt

Expresses a judgment with very strong confidence based on the circumstances.

Examples

あの足跡は熊のものにちがいない。

Those tracks must be a bear's.

これは父からの手紙に違いない。

This letter must be from my father.

Structure: Add に違いない（にちがいない） to a noun, verb, or adjective expression to convey strong conviction.
Basic usage: これは父からの手紙に違いない。 confidently identifies the letter's sender as the speaker's father.

Conviction and a verified fact
- 父からの手紙に違いない conveys the speaker's certainty based on the circumstances. The construction itself does not establish that the sender was directly verified.
Nouns and adjectives
- Do not insert だ after a noun or na-adjective in 学生に違いない or 静かに違いない. An i-adjective connects as in 高いに違いない.