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Is there a rule for when to use that instead of what?

Example: I bought two books that I'd like to read. (Some ESL students persistently use what in a sentence like this.)

Thank you!

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laura2017Is there a rule for when to use that instead of what?

The only rule is that we use them according to their meanings, i.e., as they are idiomatically used in context. The following list shows the typical usage of these words.

what, what for, what if, what about in questions.

What is your name? (without a noun)
What time is it? (with a noun)
What for? What is that used for?
What if nobody shows up?
I'd like to take a walk. What about you?

what as a fused relative (that which; the thing(s) which)

What we need is more money.
I want to do what I can to make my life comfortable.

that

That's his wife. / That's a good idea. (without a noun)
This one is bigger than that.
that man, that chair, at that time (with a noun)

that for relative clauses

She's the woman that owns the place.
I was five years old the year that Ann was born.

that adverbial

I wouldn't go that far. / It's not that far from here.

that to introduce a content clause

She said that ... / We thought that ... / I knew that ...
We pray that ... / It's annoying that ... /
We were pleased that ... / They are surprised that ...
The reason is that ... / The problem is that ...
the fact that ... / the claim that ... / the argument that ...

that of

His appearance was that of a starving man.

so that to show a result

She was so tired that she couldn't move.
This joke is so funny that you won't be able to stop laughing.
They placed the picture so that it could be seen from the doorway.

CJ

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laura2017Is there a rule for when to use that instead of what?

That is never used instead of what. The meanings and uses are completely different.

laura2017(Some ESL students persistently use what in a sentence like this.)

Their native language may lead them to do that. What is possible as a relative pronoun in sentences like this:

I'm not interested in what he said. (what = that which)

CB

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Comments  

Sometimes both are possible.

I said _____ I could.

a) that
b) what

CJ

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