Translation guide
Expresses strong certainty or conviction. Japanese uses adverbs, set phrases, and sentence-ending patterns rather than a single direct equivalent.
The speaker is completely sure about something.
A common and versatile adverb meaning 'without mistake' or 'undoubtedly'. Used in both spoken and written Japanese.
彼は間違いなく来る。
He will come without a doubt.
Without a doubt, this is the best way.
Literally 'without doubt'. Slightly more formal or literary than 間違いなく.
疑いなく、彼女が一番優秀だ。
Without a doubt, she is the most talented.
Means 'certainly' or 'surely'. Often used to acknowledge a fact before adding a contrasting point.
確かに、それは本当だ。
Without a doubt, that is true.
Adding force to a declaration, similar to 'there's no doubt that...'
Attached to a plain form clause to mean 'must be' or 'no doubt that'. Expresses strong conjecture.
彼は成功するに違いない。
He will succeed without a doubt.
あの話は本当に違いない。
That story must be true without a doubt.
Casual and emphatic. Means 'it's obvious that' or 'of course'. Used in spoken Japanese.
そんなの嘘に決まってる。
That's obviously a lie, without a doubt.
Used in essays, speeches, or formal declarations.
Literally 'there is no room for doubt'. Very formal and emphatic.
この事実に疑いの余地はない。
There is no doubt about this fact.
間違いなく is the everyday choice for 'without a doubt'. 疑いなく is more formal and less common in casual speech.
Direct translations like '疑いなしに' are unnatural. Use the patterns above instead.