know for sure

USAGE SUMMARY

The phrase "know for sure" is correct and usable in written English.
It can be used when expressing certainty or confidence about a particular fact or situation. Example: "I can't say I know for sure if the meeting is still on, but I will check with the organizer."

✓ Grammatically correct

News & Media

Academia

Human-verified examples from authoritative sources

Exact Expressions

60 human-written examples

We never know for sure.

The New York Times - Books

I didn't know for sure".

The New York Times

I don't know for sure.

Independent

I cannot know for sure.

The New York Times

We can't know for sure.

The New York Times

We'll never know for sure.

The New Yorker

To know for sure?

The Guardian - Opinion

I know for sure.

The Washington Post

We don't know for sure.

Cornell University

Do I know for sure?

Cornell University

How could they not know for sure?

The New Yorker

Expert writing Tips

Best practice

When aiming for a more formal tone, consider using alternatives such as "know with certainty" or "ascertain beyond doubt". These options can enhance the sophistication of your writing in academic or professional settings.

Common error

While "know for sure" is a common and acceptable phrase, overuse can make your writing sound repetitive. Vary your language by incorporating synonyms like "be certain", "be sure", or "ascertain" to maintain reader engagement.

Linguistic Context

The phrase "know for sure" functions as an idiomatic expression indicating certainty or a strong level of confidence in the truth of a statement. As Ludwig AI validates, this phrase is commonly used to express a firm belief based on available information or evidence.

Expression frequency: Very common

Frequent in

News & Media

68%

Academia

15%

Science

10%

Less common in

Formal & Business

5%

Encyclopedias

1%

Wiki

1%

Ludwig's WRAP-UP

In summary, the phrase "know for sure" is a grammatically sound and frequently used expression to convey a strong sense of certainty or confidence. As Ludwig AI confirms, it's versatile, fitting into various contexts from news and media to academic discussions. While alternatives like "be certain" or "ascertain" exist for more formal settings, "know for sure" remains a reliable choice for expressing conviction. To avoid monotony, it's advisable to diversify your writing with similar phrases. The consistent usage and authoritative sources underscore its validity and reliability in both written and spoken English.

More alternative expressions

Phrases that express similar concepts, ordered by semantic similarity:

know with certainty

Replaces "sure" with "certainty", emphasizing the absence of doubt.

be absolutely certain

Emphasizes the completeness of the certainty.

be completely sure

Similar to "absolutely certain", highlighting thoroughness.

ascertain beyond doubt

Focuses on eliminating any possibility of doubt through verification.

determine with assurance

Stresses the act of confidently establishing something.

establish definitively

Highlights the final and conclusive nature of the determination.

confirm unequivocally

Underscores the clarity and lack of ambiguity in the confirmation.

be positive without question

Emphasizes that there is no reason to doubt something.

have no doubt whatsoever

Focuses on the complete absence of uncertainty.

be dead certain

An idiom that is generally less formal than the original phrase.

FAQs

How can I use "know for sure" in a sentence?

You can use "know for sure" to express certainty about something. For example, "I don't "know for sure" if the meeting is still on, but I will check with the organizer".

What can I say instead of "know for sure"?

You can use alternatives like "be certain", "be sure", or "ascertain" depending on the context.

Which is correct, "know for sure" or "know for certain"?

Both ""know for sure"" and "know for certain" are correct, but "know for certain" is generally considered more formal.

What's the difference between "know for sure" and "believe"?

"Know for sure" implies a high degree of confidence based on evidence or reason, while "believe" suggests a personal conviction that may not be based on concrete proof.