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.
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...').
He is undoubtedly right.
A formal phrase meaning 'there is no room for doubt'. Used in writing or formal speech.
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.
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.
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.
That's undoubtedly a lie.
Indicates expectation or logical conclusion: 'should be' or 'undoubtedly is' based on what one knows.
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.