I know for sure

USAGE SUMMARY

"I know for sure" is a correct and usable phrase in written English.
You can use it to emphasize certainty in a statement. For example, "I know for sure that I left my keys in my car."

✓ Grammatically correct

News & Media

Academia

Human-verified examples from authoritative sources

Exact Expressions

60 human-written examples

I know for sure.

The Washington Post

Do I know for sure?

Cornell University

"Now I know for sure".

The New York Times

"That I know for sure.

The New York Times - Sports

That's all I know for sure.

The Guardian

That much I know for sure.

The Guardian - Lifestyle

Do I know for sure that this is the truth?

The New York Times

That is something that I know for sure.

The New Yorker

I know for sure everybody has to go".

The New York Times

I know for sure that it's greater than that.

Massachusetts Institute of Technology

"I know for sure the money is there," said Lloyd.

The Guardian - Sport

Expert writing Tips

Best practice

When using "I know for sure" in formal writing, consider whether a more nuanced or evidence-based statement would be more appropriate, as it can sometimes sound overly assertive.

Common error

Avoid using "I know for sure" repeatedly in a short span of writing. It can make your writing sound repetitive and less impactful. Vary your language to express certainty in different ways.

Linguistic Context

The primary grammatical function of "I know for sure" is to act as a declarative phrase used to express certainty or strong conviction about a statement. Ludwig AI examples showcase its role in conveying assurance and confidence.

Expression frequency: Very common

Frequent in

News & Media

64%

Academia

24%

Science

12%

Less common in

Formal & Business

0%

Encyclopedias

0%

Wiki

0%

Ludwig's WRAP-UP

In summary, "I know for sure" is a versatile phrase used to express a strong sense of certainty or conviction. As Ludwig AI confirms, the phrase is grammatically correct and widely used. While it appears most frequently in news and media, it is also common in academic contexts. When writing, it's best to use "I know for sure" to communicate confidence, but be mindful of potential overuse. Alternatives like "I am certain" and "I have no doubt" can add variety to your writing while maintaining a similar level of certainty.

More alternative expressions

Phrases that express similar concepts, ordered by semantic similarity:

I'm absolutely sure

Uses "absolutely" to intensify the level of certainty.

I'm completely certain

Uses "completely" to emphasize the state of being sure.

I am certain

Changes the structure to a more concise declaration of certainty.

I am positive

Substitutes "know" with "am positive", emphasizing confidence.

I am convinced

Replaces "know" with "am convinced", highlighting a deeply held belief.

I have no doubt

Shifts from a statement of knowledge to an absence of doubt.

It is certain to me

Inverts the structure to emphasize the certainty as perceived by the speaker.

I can confirm

Uses "confirm" to suggest verification of a fact.

Without a doubt, I know

Adds emphasis by placing "without a doubt" at the beginning.

It's a certainty

Expresses the statement as a definite and unarguable fact.

FAQs

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

You can use "I know for sure" to express certainty about something. For example, "I know for sure that I locked the door".

What are some alternatives to "I know for sure"?

You can use alternatives like "I am certain", "I am positive", or "I have no doubt" to express a similar level of confidence.

Is "I know for sure" too informal for academic writing?

While "I know for sure" isn't inherently incorrect, it might be perceived as informal in some academic contexts. Consider using more formal alternatives like "It is certain" or providing evidence to support your claim.

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

"I think" expresses an opinion or belief, while "I know for sure" indicates a higher level of certainty and conviction. Use "I know for sure" when you are confident in your statement and have a strong basis for your knowledge.