Difference between what and that

Jan 27, 2011

"What" is usually a question word.
by: Ola Zur

Hi,

"The book that I need" is the correct one.

Here is the explanation:

"What" is usually a question word.

Examples:
"What are you doing?"
"What are these?"
"What is your idea?"

"What" can also be used with the meaning of "the thing or things".

Here are some examples:
"What you need is a good night sleep." (= The thing you need is a good night sleep.)
"We don't know what to do." (= We don't know which things to do.)
"You know what to do." (= You know which things to do.)

"That" is used to describe and define the thing you are talking about.

For example:
"I want the pen."
"Which pen?"
"I want the pen that is on the desk."

Here's another example:
"I saw that girl."
"Which girl?"
"The girl that you invited to the party."

Now, regarding your specific sentence:
"The book what I need" would mean "the book which thing I need."
This doesn't make sense, does it?

On the other hand: "The book that I need" makes perfect sense, because you are giving a description of the book.

I hope this helps. You can also visit my English Parts of Speech page, and find more data and examples there (look for it in the pronouns section).

Ola Zur is the editor of www.really-learn-english.com, an illustrated guide to English.

Difference between what and that

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Difference between what and that

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