know for certain

USAGE SUMMARY

"know for certain" is a correct and usable phrase in written English.
You can use it when you're trying to emphasize that you have absolute certainty about something. For example, "I know for certain that she will not be attending the party tonight."

✓ Grammatically correct

News & Media

Science

Human-verified examples from authoritative sources

Exact Expressions

56 human-written examples

"It's hard to know for certain".

The New York Times

Obviously it's impossible to know for certain.

The Guardian

They may never know for certain.

The New York Times

All we can know for certain is the performance itself".

The New Yorker

there are things I know for certain about my grandfather.

Independent

I say "might be," because I don't know for certain.

The New Yorker

"We don't know for certain," I was told.

Independent

We shouldn't pretend to know for certain what we don't.

The New Yorker

I know for certain she would want that.

The New Yorker

"I can't say I do know for certain," Mackey said.

The New York Times - Sports

Only she and the president may know for certain.

The New York Times

Expert writing Tips

Best practice

Use "know for certain" when you want to express a strong sense of conviction or certainty about something, leaving no room for doubt.

Common error

While "know for certain" is a valid phrase, avoid overusing it. Vary your language by using synonyms like "be absolutely sure" or "be completely confident" to maintain reader engagement.

Linguistic Context

The phrase "know for certain" functions as a declarative expression used to convey a state of absolute certainty or conviction. It asserts that the speaker or writer possesses unquestionable knowledge about a particular fact or situation. This is supported by Ludwig's examples that show it's often used to introduce a statement of fact.

Expression frequency: Very common

Frequent in

News & Media

67%

Science

16%

Formal & Business

8%

Less common in

Academia

5%

Encyclopedias

2%

Wiki

2%

Ludwig's WRAP-UP

In summary, "know for certain" is a versatile phrase used to express a high degree of confidence or certainty. As Ludwig AI confirms, it's grammatically sound and widely applicable. It's prevalent in news and media, as well as scientific contexts, serving to eliminate doubt and assert facts. While alternatives exist to avoid repetition, "know for certain" remains a strong and clear way to communicate unwavering conviction.

More alternative expressions

Phrases that express similar concepts, ordered by semantic similarity:

be absolutely sure

Emphasizes the absence of doubt, similar to knowing something for certain.

be completely confident

Focuses on the feeling of assurance, akin to knowing for certain.

have no doubt

Highlights the lack of uncertainty, resembling the conviction of knowing for certain.

be one hundred percent sure

Uses a percentage to express complete certainty, similar to knowing for certain.

be positive

Indicates a firm belief, aligning with the assurance of knowing for certain.

ascertain without a doubt

Emphasizes the process of finding something out while also ensuring certainty.

determine with certainty

Focuses on the act of establishing something definitively, akin to knowing for certain.

establish beyond question

Highlights that something is confirmed and cannot be challenged.

be convinced beyond any doubt

Highlights the state of having been influenced to be completely certain.

be sure beyond a shadow of a doubt

Stresses the total absence of doubt, similar to knowing something with absolute certainty.

FAQs

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

You can use "know for certain" to express a strong conviction about something, for example: "I "know for certain" that the meeting is scheduled for tomorrow."

What are some alternatives to "know for certain"?

Alternatives include phrases like "be absolutely sure", "be completely confident", or "have no doubt". The best choice depends on the specific context.

Is it more formal to say "know for certain" or "know for sure"?

"Know for certain" and "know for sure" are both acceptable, but "know for certain" tends to be perceived as slightly more formal than "know for sure".

Can I use "know for certain" in academic writing?

Yes, "know for certain" is appropriate for academic writing when you want to emphasize that something has been definitively established or proven.