Translation guide
Expresses strong certainty that something is true or will happen. Japanese often conveys this through adverbs, sentence-ending particles, or set phrases rather than a single direct equivalent.
To state that something is definitely the case, based on evidence or strong belief.
The most common and versatile adverb meaning 'without mistake' or 'undoubtedly'. Used in both spoken and written Japanese.
彼は間違いなく成功するだろう。
He will undoubtedly succeed.
This is undoubtedly his best work.
Means 'certainly' or 'surely'. Often used when acknowledging a fact, sometimes with a concessive nuance ('it is true that...').
確かに彼の言う通りだ。
He is undoubtedly right.
A formal phrase meaning 'there is no room for doubt'. Used in writing or formal speech.
この証拠には疑いの余地はない。
There is undoubtedly no room for doubt in this evidence.
Means 'without fail' or 'definitely'. Emphasizes inevitability or a strong promise. Often used for future events.
彼は必ず来る。
He will undoubtedly come.
To add a nuance of 'undoubtedly' at the end of a sentence, often in spoken Japanese.
Attached to a plain form clause to mean 'must be' or 'undoubtedly is'. Expresses strong conviction based on reasoning.
彼は疲れているに違いない。
He must be tired, undoubtedly.
A more colloquial version of 〜に違いない, meaning 'it's obvious that' or 'undoubtedly'. Common in casual speech.
そんなの嘘に決まってる。
That's undoubtedly a lie.
Indicates expectation or logical conclusion: 'should be' or 'undoubtedly is' based on what one knows.
彼なら知っているはずだ。
He undoubtedly knows (given who he is).
Direct translations like '疑いなく' (utagainaku) exist but are less common and can sound stiff. Use 間違いなく or sentence patterns for natural expression.