N4 grammar
〜に違いない
It must be
Formationplain form or noun + に違いない
に違いない is the strongest of the guessing patterns, close to English it must be. You use it when the evidence leaves you no room for doubt. It leans formal, so speech often prefers きっと with a plain sentence.
Examples
〜に違いない is marked in each sentence. Tap any word for its dictionary entry.
何か変なものを感じ取ったに違いない。
She must have sensed something odd.
彼はどこかの会社の重役に違いない。
One must be an executive in some company.
病気だったに違いない。
He must have been ill.
出火したのは職員が帰宅した後に違いない。
The fire must have broken out after the staff had gone home.
お百姓さんはそれを聞いて喜ぶに違いない。
The farmers must be happy to hear that.