not sure

USAGE SUMMARY

"not sure" is a perfectly acceptable phrase and can be used in written English.
For example, you might write "I am not sure if I understand the question correctly."

✓ Grammatically correct

News & Media

Science

Academia

Human-verified examples from authoritative sources

Exact Expressions

60 human-written examples

"Not sure, not sure.

The Guardian - Sport

A.I'm not sure.

The New York Times

So I'm not sure.

The New York Times

"Not sure," Kiehl said.

The New Yorker

I'm honestly not sure".

The New York Times - Sports

I'm not sure, either.

The New Yorker

I'm not sure which.

Independent

"But I'm not sure".

The New York Times

"Because I'm not sure.

The New York Times

"I'm not sure what.

The New York Times - Health

"We're not sure yet".

The New York Times

Expert writing Tips

Best practice

When writing, consider the degree of uncertainty you want to convey. If you want to express strong doubt, alternatives like "doubtful" or "questionable" might be more suitable.

Common error

While "not sure" is acceptable, overuse in formal writing can make you sound less confident. Instead, try using more precise alternatives like "uncertain", "undetermined", or providing specific reasons for your uncertainty.

Linguistic Context

The phrase "not sure" functions as an adjective phrase expressing uncertainty, doubt, or a lack of definite knowledge or opinion. As Ludwig AI confirms, the phrase is perfectly acceptable and widely used. It often modifies a subject to indicate their state of uncertainty.

Expression frequency: Very common

Frequent in

News & Media

58%

Science

22%

Academia

20%

Less common in

Formal & Business

0%

Encyclopedias

0%

Wiki

0%

Ludwig's WRAP-UP

In summary, "not sure" is a common and acceptable phrase used to express uncertainty or a lack of knowledge. Ludwig AI confirms its validity, highlighting its widespread use in various contexts. While generally neutral in register, more formal alternatives like "uncertain" may be preferred in academic or professional settings. This phrase is grammatically correct and used across various sources, from news media to scientific publications. To enhance clarity and confidence in your writing, consider the context and choose the most appropriate expression of uncertainty.

More alternative expressions

Phrases that express similar concepts, ordered by semantic similarity:

unsure

Similar to "not sure", but can sometimes imply a slightly stronger feeling of doubt.

not certain

A direct synonym, often used in more formal contexts.

uncertain

A more formal synonym expressing doubt or lack of sureness.

not convinced

Indicates a lack of persuasion or belief.

doubtful

Implies a degree of skepticism or disbelief.

in doubt

A more formal way of expressing uncertainty.

undetermined

Expresses that something has not yet been definitely decided or established.

questionable

Suggests that something is open to doubt or debate.

haven't decided

Implies that a decision is pending due to uncertainty.

on the fence

An idiomatic expression indicating indecision.

FAQs

How can I use "not sure" in a sentence?

You can use "not sure" to express uncertainty or lack of knowledge. For example, "I'm "not sure" if I locked the door" or "She said she was "not sure" what to do next".

What can I say instead of "not sure" to sound more formal?

To sound more formal, you can use alternatives such as "uncertain", "undetermined", or "doubtful". For example, instead of "I'm "not sure"", you could say "I am uncertain about the matter".

Is it correct to say "unsure" instead of "not sure"?

Yes, "unsure" is a perfectly acceptable alternative to "not sure". They are largely interchangeable, although "unsure" may sometimes carry a slightly stronger implication of doubt.

What's the difference between "not sure" and "not certain"?

"Not sure" and "not certain" are very similar in meaning. However, "not certain" might be perceived as slightly more formal than "not sure". Both express a lack of complete confidence or knowledge.