Translation guide
The English verb "assume" has several distinct meanings. This guide helps learners choose the right Japanese expression based on the intended meaning: taking on a role or responsibility, supposing something without proof, or adopting a particular attitude or appearance.
To begin to have a particular job, position, or responsibility.
Used when formally assuming a position or office, such as a presidency or directorship.
彼は来月、社長に就任する。
He will assume the position of president next month.
General term for taking on a task, responsibility, or role. Can be used in both formal and casual contexts.
彼女はそのプロジェクトのリーダーを引き受けた。
She assumed the role of leader for the project.
To shoulder or bear a responsibility, often with a sense of duty. Slightly more literary.
彼は重い責任を担っている。
He assumes a heavy responsibility.
To think that something is true or will happen, although you have no proof.
To assume for the sake of argument or as a premise. Common in logical or hypothetical contexts.
彼が有罪だと仮定しよう。
Let's assume he is guilty.
To assume firmly, often incorrectly or without basis. Implies a subjective belief.
彼女は私が嘘をついていると思い込んでいる。
She assumes I'm lying.
To jump to a conclusion and act on that assumption, often with a negative nuance.
彼は私が失敗すると決めてかかっている。
He assumes I will fail.
To guess or infer based on available information. Less strong than 'assume' in English, but often used in similar contexts.
警察は彼が犯人だと推測している。
The police assume he is the culprit.
A grammatical pattern meaning 'to assume/suppose that...'. Used in hypothetical or conditional statements.
彼が来ないとすると、計画を変えなければならない。
Assuming he doesn't come, we'll have to change the plan.
To begin to have a particular quality, appearance, or name, often deliberately or temporarily.
To put on an appearance or pretense; to feign. Often used for attitudes or emotions.
彼は平静を装った。
He assumed an air of calmness.
To take on a certain quality or characteristic, often gradually or inherently.
To assume a name; to call oneself by a particular name.
While 仮定する is correct for logical assumptions, using it for casual guesses like 'I assume you're busy' sounds unnatural. Use 思う (to think) or だろう (probably) instead.
忙しいだろうね。
I assume you're busy.
Both mean to assume, but 思い込む focuses on a fixed belief (often mistaken), while 決めてかかる implies acting on that assumption, often confrontationally.
The words assumed a sarcastic tone.
He assumed a false name.