assume + noun
Accept something as true
Use assume directly before a noun.
They assumed the risk immediately.
Assume: by or for?
Assume normally takes a direct object or a that-clause. “Assume by” is not a standard pattern after the verb, while “assume for” appears in fixed expressions such as “assume responsibility for”.
Quick answer
Which preposition is correct with assume?
Use assume without a preposition in most cases: assume a fact, assume that something is true. “Assume by” is not an idiomatic verb-preposition combination. “Assume for” is only natural when for belongs to a following noun or purpose phrase.
We assumed that the train was delayed.
She assumed responsibility for the project.
She assumed responsibility for the project.
Choose the pattern by meaning
These forms are not interchangeable. Choose the construction by meaning, not by which preposition appears most often.
assume that + clause
State an expectation or belief
Use a that-clause for opinions or expectations.
I assume that everyone has arrived.
assume responsibility for + noun
Take duty or control
For belongs to the noun responsibility, not directly to assume.
He assumed responsibility for customer support.
assume by + method
By as a separate adjunct
By can describe a method in the sentence, not a fixed pattern with assume.
Do not assume by appearance alone.
See the difference in context
The same subject can take different constructions because each sentence answers a different question.
Construction
Example
Meaning
assume + noun
They assumed control of the company.
Standard use without a preposition.
assume for
She assumed responsibility for hiring.
Natural only when for belongs to the following noun.
assume by
We cannot assume by appearances.
By expresses the basis of the assumption, not a fixed verb pattern.
Common mistakes
Some combinations appear in real text but do not mean what learners often assume.
Using assume by as a fixed pattern
Assume does not normally take by directly after it.
✕ We assumed by the data. ✓ We made assumptions based on the data.Adding an unnecessary preposition
Assume usually takes a direct object.
✕ They assumed for his absence. ✓ They assumed his absence was temporary.Quick practice
Choose the expression that matches the intended meaning.
1. We cannot ___ appearances alone.
2. She assumed responsibility ___ training.
3. I assume ___ the meeting starts at nine.
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Frequently asked questions
Is “assume by” correct?
Not as a standard verb-preposition pattern. By may introduce the basis or method in a larger sentence.
Can I say “assume for”?
Only in expressions such as “assume responsibility for something”.
Does assume need a preposition?
Usually no. It commonly takes a direct object or a that-clause.
Related preposition guides
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