Translation guide
The English word "doubt" covers a range of meanings from uncertainty and skepticism to suspicion and disbelief. In Japanese, different words and expressions are used depending on whether you are expressing personal uncertainty, questioning a fact, suspecting someone, or stating that something is unlikely. This guide helps learners choose the most natural Japanese expression for each nuance.
Expressing that you are not sure about something, or that you have doubts about your own knowledge or ability.
A general noun meaning 'doubt' or 'question'. Often used in phrases like 疑問に思う (to have doubts about something). It is neutral and can be used in both spoken and written contexts.
彼の説明には疑問がある。
I have doubts about his explanation.
その計画に疑問を感じる。
I have doubts about that plan.
Literally 'have no confidence'. This is the most natural way to express self-doubt about one's ability or knowledge.
試験に合格できるか自信がない。
I doubt I can pass the exam.
Means 'to think something is doubtful/questionable'. Used when you are skeptical about a statement or claim.
彼の言うことは少し疑わしいと思う。
I think what he says is a bit doubtful.
A set phrase meaning 'half in doubt, half believing'. Used when you are not fully convinced.
そのニュースを聞いて半信半疑だった。
I was in doubt about that news.
Expressing that you think something may not be true or correct.
The most direct verb for 'to doubt' or 'to suspect'. It can be used for doubting facts, statements, or people's honesty. Be careful: when used with a person, it often implies suspicion of wrongdoing.
私は彼の言葉を疑っている。
I doubt his words.
その話の真実性を疑う。
I doubt the truth of that story.
Means 'to think something is suspicious/doubtful'. More colloquial than 疑う and often used in everyday conversation.
あの人の言い訳は怪しいと思う。
I doubt that person's excuse.
A phrase meaning 'doubtful whether it's true'. Useful when you want to express skepticism without directly accusing someone.
その情報は本当かどうか疑わしい。
I doubt whether that information is true.
Expressing that you believe someone may have done something bad or dishonest.
The same verb as above, but when the object is a person, it strongly implies suspicion of a crime or misdeed. Often used in the passive form 疑われる (to be suspected).
警察は彼を犯人だと疑っている。
The police suspect him of being the culprit.
彼は嘘をついていると疑われた。
He was suspected of lying.
A verb meaning 'to suspect' or 'to be suspicious of'. Slightly more formal and less common in casual speech than 疑う.
A noun meaning 'suspicion' (often in a legal or formal context). Used in phrases like 嫌疑をかける (to cast suspicion on someone).
Saying that you think something probably won't happen or isn't true.
A pattern meaning 'I can't think that...' or 'I doubt that...'. It is a natural way to express disbelief or strong doubt about a statement.
彼がそんなことをするとは思えない。
I doubt he would do such a thing.
明日雨が降るとは思えない。
I doubt it will rain tomorrow.
A strong expression meaning 'there is no way that...' or 'it cannot be that...'. It conveys a high degree of certainty that something is not true.
彼が知らないはずがない。
I doubt he doesn't know. (lit. There's no way he doesn't know.)
Similar to はずがない, meaning 'there is no reason that...' or 'it's impossible that...'. Slightly more logical/rational in nuance.
彼女がそんなミスをするわけがない。
I doubt she would make such a mistake. (lit. There's no reason she would make such a mistake.)
Expressing hesitation or reconsideration about a choice or plan.
Means 'to have hesitation/doubt' about a decision. It implies you are wavering or unsure.
その仕事を引き受けるかどうか、まだ迷いがある。
I still have doubts about whether to accept that job.
Similar to 迷い, but often implies a more emotional hesitation or reluctance.
彼に真実を話すことにためらいがある。
I have doubts about telling him the truth.
English speakers often say 'I doubt it' as a casual response. In Japanese, directly translating this as それを疑う sounds unnatural and overly strong. Instead, use phrases like そうは思わない (I don't think so), それはないと思う (I don't think that's the case), or 多分違うと思う (I think it's probably not).
疑う (utagau) often implies active suspicion or distrust, especially toward a person. 疑問に思う (gimon ni omou) is more about intellectual doubt or questioning the validity of something, without necessarily implying bad intent. Use 疑問に思う when you simply find something questionable or unclear.
彼が有罪であることは疑いない。
There is no doubt that he is guilty.
彼が来るかどうか疑わしい。
I doubt if he will come.
彼の行動を怪しむ。
I am suspicious of his behavior.
He is under suspicion of theft.