Translation guide
In Japanese, expressing supposition involves various grammatical patterns and words that convey conjecture, assumption, or guesswork. The choice depends on the level of certainty, formality, and whether the supposition is based on evidence or intuition.
Expressing that something is probably the case, based on reasoning or intuition.
The most common way to express supposition in casual speech. It indicates the speaker's conjecture. In formal contexts, use 〜でしょう.
明日は雨だろう。
It will probably rain tomorrow.
彼はもう帰っただろう。
He has probably already gone home.
The polite form of 〜だろう, used in formal situations or when speaking politely.
明日は雨でしょう。
It will probably rain tomorrow.
この問題は難しいでしょう。
This problem is probably difficult.
Expresses possibility or uncertainty, similar to 'might' or 'maybe'. Less certain than 〜だろう.
彼は来ないかもしれない。
He might not come.
それは本当かもしれない。
That might be true.
Indicates a strong supposition based on logical reasoning or expectation, similar to 'should' or 'ought to'.
彼はもう着いているはずだ。
He should have arrived by now.
この薬を飲めば治るはずだ。
You should get better if you take this medicine.
Expresses a strong conviction or supposition, similar to 'must be' or 'no doubt'. More emphatic than 〜はずだ.
あの人は日本人に違いない。
That person must be Japanese.
彼は嘘をついているに違いない。
He must be lying.
Expressing a guess based on what you see or hear, often using sensory evidence.
Attached to verb stems or adjective stems to indicate that something looks or seems like it will happen or is the case, based on direct evidence.
雨が降りそうだ。
It looks like it's going to rain.
このケーキはおいしそうだ。
This cake looks delicious.
Indicates a supposition based on sensory or situational evidence, similar to 'it seems that'. More subjective than 〜そうだ.
誰かいるようだ。
It seems like someone is there.
彼は疲れているようだ。
He seems to be tired.
A more colloquial version of 〜ようだ, used in casual conversation to express supposition based on evidence.
あの店、閉まってるみたいだ。
It looks like that store is closed.
彼女は怒ってるみたいだ。
She seems angry.
Expressing a supposition about a hypothetical or counterfactual situation.
Used to present a hypothetical supposition, meaning 'if we suppose that...' or 'assuming that...'.
彼が来るとしたら、何時に来るだろう。
If he were to come, what time would he arrive?
それが本当だとしたら、大変なことだ。
If that were true, it would be serious.
Similar to 〜としたら, but slightly more formal or written. Used for hypothetical suppositions.
彼が犯人だとすれば、動機は何だろう。
If he is the culprit, what would his motive be?
Another variation for hypothetical supposition, often interchangeable with 〜としたら and 〜とすれば.
明日雨だとすると、試合は中止だ。
If it rains tomorrow, the game will be canceled.
Using adverbs to express uncertainty or conjecture.
The most common adverb for 'probably' or 'maybe'. Often used with 〜だろう/でしょう.
多分、彼は来るだろう。
He will probably come.
多分、大丈夫です。
It's probably okay.
A more formal or written word for 'probably' or 'perhaps', often implying a higher degree of likelihood.
Expresses a lower probability, similar to 'maybe' or 'possibly'. Often used with 〜かもしれない.
〜だろう indicates a higher degree of certainty than 〜かもしれない. Use 〜だろう when you are fairly confident, and 〜かもしれない when you are less sure or want to sound more tentative.
彼は来るだろう。
He will probably come. (I'm quite sure.)
彼は来るかもしれない。
He might come. (I'm not sure.)
〜そうだ is used for immediate, sensory-based guesses (looks like it's about to rain). 〜ようだ/〜みたいだ is used for more subjective inferences based on evidence (seems like someone is there). In casual speech, 〜みたいだ is more common than 〜ようだ.
恐らく、彼は成功するだろう。
He will probably succeed.
Maybe he won't come.