adverb
without fail; undoubtedly; for sure
Expresses strong certainty that something will happen or is true. Often used when the speaker is confident based on evidence or expectation.
彼は間違いなく来るよ。
He'll definitely come.
この方法なら間違いなく成功する。
With this method, we'll succeed without a doubt.
Derived from 間違い (mistake) + なく (adverbial form of ない, 'not existing'), literally 'without mistake'.