Translation guide
In Japanese, expressing an assumption depends on the level of certainty, the basis for the assumption, and whether it is about the past, present, or future. Common patterns include はず for logical expectations, だろう/でしょう for conjecture, and と思う for personal belief. The choice of expression also reflects formality and the speaker's confidence.
Expressing that something is expected to be the case based on reasoning, common sense, or prior information. Often translated as 'should' or 'ought to'.
Indicates a strong assumption based on logical reasoning or factual knowledge. The speaker is confident that something is true or will happen. Used for both present and past assumptions.
He should have arrived by now.
If you take this medicine, you should get better.
Used to state a conclusion or assumption that naturally follows from a given situation or explanation. It often translates to 'so that means...' or 'it follows that...'.
He lived in Japan for 10 years, so it makes sense that his Japanese is good.
Expresses a strong conviction or assumption, often based on intuition or circumstantial evidence. Similar to 'must be' or 'no doubt'.
Seeing that smile, he must be happy.
Expressing a personal guess or prediction without strong evidence. Often translated as 'probably', 'I think', or 'maybe'.
Plain form conjecture. Used in casual speech or writing to express a guess. The polite form is でしょう.
It will probably rain tomorrow.
Polite form of conjecture. Commonly used in formal conversation, news, and polite writing.
It will probably rain tomorrow.
Expresses a possibility or uncertain assumption. 'Might' or 'may'. Less confident than だろう/でしょう.
He might not come.
Literally 'I think that...'. Used to express personal assumption or belief. Can be softened with ～気がする (I have a feeling that...).
I think he will succeed.
Expressing what you assume happened or was true in the past, often based on evidence or reasoning.
Assumption about a past event that should have happened according to logic or expectation.
He should have departed yesterday.
Strong assumption about a past event. 'Must have done'.
Possibility about a past event. 'Might have done'.
He might have already gone home.
Setting up a hypothetical situation or condition for the sake of argument. Often used in formal or academic contexts.
The act of taking on a position, role, or responsibility. This is a different sense of 'assumption'.
はず indicates a logical conclusion based on evidence or reasoning (high certainty). だろう/でしょう is a conjecture or guess (moderate certainty). かもしれない expresses possibility (low certainty). Choose based on how confident you are.
He should come (there's a reason).
He will probably come (guess).
He might come (possibility).
English 'assume' can be translated as 仮定する (to hypothesize) or 思い込む (to take for granted), but these are not always natural. For everyday assumptions, use patterns like はず or と思う instead of trying to directly translate 'assume'.
I assumed he would come.
He must have known the secret.
He assumed the role of leader for the project.