Translation guide
Expressing that something is definitely true or will definitely happen. Japanese often uses adverbs, sentence-ending particles, or set phrases rather than a single noun equivalent.
The speaker wants to assert that a fact or statement is undoubtedly correct.
Adverb meaning 'certainly' or 'surely', often used to agree with a statement or acknowledge a fact.
確かに、それは正しいです。
Certainly, that is correct.
Adverb meaning 'without a doubt' or 'definitely'. Stronger than 確かに.
間違いなく、彼が勝つでしょう。
Without a doubt, he will win.
Phrase attached to nouns, adjectives, or verbs meaning 'must be' or 'no doubt that'. Expresses strong conviction.
彼は病気に違いない。
He must be sick.
Colloquial phrase meaning 'it's obvious that' or 'of course'. Used in casual speech.
そんなの嘘に決まってる。
That's obviously a lie.
The speaker wants to convey that something will definitely happen.
Adverb meaning 'without fail' or 'definitely'. Used for future events or obligations.
必ず成功します。
I will definitely succeed.
Adverb meaning 'absolutely' or 'definitely'. Often used with negative for 'never'.
絶対に忘れないでください。
Please definitely don't forget.
Phrase meaning 'should be' or 'ought to be', based on logical expectation. Less absolute than 必ず.
彼はもう着いているはずだ。
He should have arrived by now.
The speaker wants to check if something is certain or to express doubt.
Pattern meaning 'whether or not'. Used to embed a question about certainty.
彼が来るかどうか確かめてください。
Please check whether he will come.
Simple phrase meaning 'Really?' to express doubt or seek confirmation.
本当に？信じられない。
Really? I can't believe it.
Referring to certainty as a concept or quality.
Formal noun meaning 'certainty' or 'reliability'. Used in technical or written contexts.
その情報の確実性は低い。
The certainty of that information is low.
Noun meaning 'conviction' or 'firm belief'. Often used in the phrase 確信がある (to be certain).
English 'certainty' as a noun is rarely used in natural Japanese conversation. Instead, use adverbs like 確かに or 必ず, or phrases like に違いない to express the idea.
必ず implies a natural or logical inevitability, while 絶対に is more subjective and emphatic. 絶対に is common in both positive and negative sentences, but 必ず is less natural with negatives.
彼が来るという確実性はない。
There's no certainty that he will come.
Formal; in conversation, 彼が来るかどうかわからない is more natural.
彼の無実を確信している。
I am certain of his innocence.