Translation guide
How to express uncertainty in Japanese, from vague guesses to formal doubt.
The speaker is unsure about something and wants to convey that feeling.
A common pattern meaning 'I don't know whether...'. Attach to a plain form clause.
彼が来るかどうかわからない。
I'm not sure whether he will come.
I'm not sure if that's true.
Means 'uncertain' or 'unreliable'. Often used in formal or written contexts.
結果はまだ不確かです。
The outcome is still uncertain.
Literally 'I have no confidence', used to express uncertainty about one's own knowledge or ability.
その答えに自信がない。
I'm not confident about that answer.
Expresses possibility or uncertainty, like 'might' or 'maybe'. Attach to plain form.
雨が降るかもしれない。
It might rain.
Talking about an external state of uncertainty, not just personal feeling.
Means 'opaque' or 'uncertain', often used for future prospects or situations.
経済の見通しは不透明だ。
The economic outlook is uncertain.
Means 'indeterminate' or 'uncertain', used in technical or formal contexts.
Means 'not clear' or 'vague', used for situations or information.
彼の態度ははっきりしない。
His attitude is uncertain.
Used in writing, news, or technical discussions to denote uncertainty.
The noun form meaning 'uncertainty', common in academic or economic contexts.
不確実性を減らす必要がある。
We need to reduce uncertainty.
Similar to 不確実性 but more often used in physics or philosophy (e.g., Heisenberg's uncertainty principle).
不確定性原理
uncertainty principle
Using adverbs to convey a sense of uncertainty in a statement.
The English noun 'uncertainty' is often best expressed with verbs or adjectives in Japanese, like わからない or 不確かだ. Using the noun 不確実性 is mostly for formal writing.
たぶん is an adverb meaning 'probably', while かもしれない is a sentence-ending pattern meaning 'might'. They can be combined: たぶん〜かもしれない.
たぶん彼は来るかもしれない。
He might probably come.
不確定要素が多い。
There are many uncertain factors.
おそらく彼は来ないだろう。
He probably won't come.
もしかすると雨が降るかもしれない。
Perhaps it might rain.