what that is

USAGE SUMMARY

The phrase "what that is" is correct and usable in written English.
It can be used when seeking clarification or asking for an explanation about something. Example: "Can you please explain what that is in more detail?"

✓ Grammatically correct

News & Media

Academia

Wiki

Human-verified examples from authoritative sources

Exact Expressions

58 human-written examples

That's basically what that is".

The New York Times - Sports

I have no idea what that is".

BMJ Open

Remember what that is?

Massachusetts Institute of Technology

"That's what that is to me".

The New Yorker

We know what that is like.

The New York Times

He said: 'I know what that is.

The New York Times - Magazine

"That's what that is?" he said.

The New York Times

"The British know what that is.

The New York Times - Sports

What that is, I don't know".

The New York Times - Sports

Human-verified similar examples from authoritative sources

Similar Expressions

2 human-written examples

For what that's worth.

The New Yorker

That's what — that was her instrument".

The New York Times - Arts

Expert writing Tips

Best practice

Ensure there is a clear antecedent for 'that' so the reader understands exactly which object or idea is being identified.

Common error

Do not use "what that is" as a standalone direct question. In a direct inquiry, you must invert the subject and verb to say "What is that?". Use the phrase "what that is" only when it is part of a larger statement, such as "I don't know what that is".

Linguistic Context

The phrase "what that is" primarily functions as a noun clause (also known as a complement clause) or an indirect question fragment. In the examples provided by Ludwig AI, it often acts as the object of a verb such as 'know', 'explain', 'understand' or 'tell'. Syntactically, it consists of a relative pronoun ('what'), a demonstrative pronoun ('that') and the linking verb ('is').

Expression frequency: Very common

Frequent in

News & Media

60%

Academia

25%

Wiki

10%

Less common in

Science

3%

Formal & Business

1%

Social Media

1%

Ludwig's WRAP-UP

The phrase "what that is" is a robust and essential component of the English language used for identifying and defining subjects within a discourse. According to Ludwig AI data, it is most frequently utilized in complex sentence structures as an indirect question or a noun clause. Its presence in high-authority sources such as The New York Times and MIT confirms that it is acceptable in both high-level academic explanations and everyday reporting. Writers should be careful not to confuse it with the direct question format "What is that?", but otherwise, it is a versatile tool for providing clarity and context. Whether you are explaining a technical term or expressing curiosity about a new concept, "what that is" serves as a clear linguistic bridge between a pronoun and its definition.

More alternative expressions

Phrases that express similar concepts, ordered by semantic similarity:

what it is

Uses a generic pronoun instead of a demonstrative one for a slightly more neutral tone

what that means

Focuses specifically on the definition or implication of the subject

what that represents

Suggests a symbolic or broader connection to the object

what is meant by that

Uses a passive construction to clarify a previous statement

the nature of that

Provides a more formal and analytical approach to describing the subject

what that signifies

Elevates the register to a more academic or semiotic level

what that involves

Emphasizes the process or components of the thing being discussed

what that entails

More formal version focused on the consequences or requirements of the subject

its identity

Uses a possessive noun phrase for a more direct identification

that specific thing

A more colloquial and descriptive way to point to the subject

FAQs

How do I use "what that is" in a sentence?

You can use it in dependent clauses to provide explanation, such as "I will explain "what that is"" or "She has no idea "what that is"".

Is "what that is" or "what is that" correct?

Both are correct but serve different functions. Use "what is that" for direct questions. Use "what that is" for indirect statements or relative clauses within a larger sentence.

What is a better way to say "what that is"?

Depending on the context, you might use more specific alternatives like "what it is", "what that means" or "the nature of that".

Can I start a sentence with "what that is"?

Yes, it can function as a subject clause, for example: ""What that is" remains a mystery to the investigators."