Assume
verbBase assume · Past assumed · Past Participle assumed · Present Participle assuming · 3rd person assumes
Definition
1. (verb) To believe something is true without having proof — to accept something as a fact without checking.
2. (verb) To take on a responsibility, role, or position — especially one that carries power or authority.
2. (verb) To take on a responsibility, role, or position — especially one that carries power or authority.
Context Alive
You text your friend asking if she's coming to the party tonight and she doesn't reply for three hours. You assume she's busy at work and don't think much of it. Later she calls and says she was actually at the hospital with her mum — nothing serious, but she couldn't look at her phone. You feel bad for not checking on her sooner and remind yourself not to just assume things next time.
Meanings
2 meanings 1 To Believe Something Without Proof (Verb) Very Common ▼
This meaning is about accepting something as true in your mind without actually knowing for sure — filling in the blanks with your own guess. Imagine you send your boss a proposal and he doesn't reply for a week. You assume he hated it and start worrying — but then he messages saying he loved it and was just on holiday. This is describing the act of drawing a conclusion without evidence. You might say "I assumed you already knew" when you find out someone didn't have information you thought was obvious, or someone could say "don't assume the worst" to a friend who's jumping to negative conclusions without facts. Or picture a tourist walking into a restaurant in Japan and assuming the menu will have English — but there's not a single word they can read. The word suggests a gap between what you believe and what's actually true.
✏️ Assume often carries a warning tone — "don't assume" is something you hear a lot because assumptions lead to misunderstandings. The famous saying is: "when you assume, you make an ass out of u and me" — a wordplay on the spelling. The noun form assumption is equally common: "that's a dangerous assumption" or "based on the assumption that..."
2 To Take On a Role or Responsibility (Verb) Common ▼
This meaning is about officially taking on a new position, duty, or level of authority — stepping into a role that carries weight. Imagine a vice president who assumes the presidency after the president resigns — she steps into the top job and takes on all its responsibilities overnight. This is describing a formal transfer of power or duty. You might read that "the new CEO assumed her role on Monday" in a company announcement, or someone could say "he assumed command of the troops" in a military context when a new officer takes charge. Or think about an older sibling who assumes the role of parent after their mother falls ill — cooking, cleaning, paying bills — even though nobody officially gave them the job. The word suggests the responsibility is significant and the person accepts it fully.
✏️ This meaning is more formal and appears in news, business, politics, and military language. Assume office, assume command, assume responsibility, and assume control are all fixed phrases. It sounds more serious than "take on" — saying "she assumed the role" carries more weight than "she took on the role."
Common Patterns
Believing Without Proof
assume (that) + clause → to believe something is the case without checking
I assumed you were coming, so I bought you a ticket.
don't assume → a warning not to jump to conclusions
Don't assume he's angry just because he hasn't replied.
it's safe to assume (that) → it's reasonable to believe this is true based on the situation
It's safe to assume the meeting has been cancelled since nobody's here.
Taking On a Role
assume + role / position / office → to officially take on a new job or authority
She assumed the role of director last month.
assume responsibility / control → to take charge of something important
The military assumed control of the region after the crisis.
assume command → to take over leadership — especially in military or emergency contexts
The lieutenant assumed command after the captain was injured.
Collocations
10 collocationsassume the worst
to believe the most negative outcome without evidence
safely assume
to make a reasonable guess based on what you know
wrongly assume
to believe something that turns out to be incorrect
just assume
to casually believe something without thinking too deeply
assume responsibility
to formally accept that something is your duty
assume control
to take charge of a situation or organisation
assume office
to officially begin serving in a political or leadership position
assume a role
to step into a new position or function
assume the position
to take up a specific role or stance
based on the assumption
built on a belief that may or may not be true
Example Sentences
10 examples
1
I assumed you already knew about the meeting — sorry I didn't tell you.
I thought you were already aware of the meeting — I apologise for not mentioning it.
2
Don't assume the worst — there could be a perfectly good explanation.
Don't jump to the most negative conclusion — there might be a simple reason.
3
She assumed the role of team leader after the previous one resigned.
She stepped into the team leader position after the person before her quit.
4
Everyone assumed he was rich because he wore expensive suits.
People believed he was wealthy because of his designer clothes.
5
It's safe to assume the flight will be delayed given the weather conditions.
It's reasonable to expect the flight will be late considering how bad the weather is.
6
The vice president assumed office after the president stepped down.
The vice president took over the top job once the president resigned.
7
I wrongly assumed that the shop would be open on Sunday.
I mistakenly thought the shop would be trading on Sunday.
8
He assumed full responsibility for the mistake and apologised to the client.
He accepted complete blame for the error and said sorry to the customer.
9
You can't just assume people agree with you — you need to ask them.
You can't simply take it for granted that people share your opinion — you have to check.
10
The plan was based on the assumption that costs would stay the same — but they didn't.
The plan relied on the belief that prices wouldn't change — but they went up.
Synonyms & Antonyms
6 items
Synonymspresume
very similar — slightly more formal and implies a bit more confidence in the belief
suppose
softer and more tentative — less certain than assume
take on
works for the 'role/responsibility' meaning — more informal
Antonymsverify
to check the facts instead of guessing — the opposite of assuming
confirm
to make sure something is true before accepting it
relinquish
to give up a role or responsibility — the opposite of assuming one