5

The sentence goes one of these two ways:

"He knows WHAT other teachers don't know"

or perhaps:

"He knows things THAT others teachers don't"

Which is better to use - WHAT or THAT? Are they both grammatically acceptable?

  • 1
    I might use the first one if I was explaining why he was such a great teacher. I might be more inclined to use the second one if I was explaining that he was aware of some impending shakeup at the school before other teachers knew the facts. But that's a blurry dividing line. – J.R. Sep 17 '13 at 15:57
5

Both are grammatical, but they mean somewhat different things.

He knows what other teachers don't know.

In this the clause what other teachers don't know is a "free relative clause", which acts all-by-itself as a noun clause. In this case it acts as the Direct Object of the verb knows.

He knows [DirObj what other teachers don't know.]

In another sentence it might act as the Subject:

[Subj What other teachers don't know] is how to communicate with their students.

If it is not specifically modified, it will be understood to mean everything which other teachers don't know.

He knows all the things which other teachers don't know.


He knows things that other teachers don't know.

In this the clause that other teachers don't know is a "bound relative clause". It might also be written which other teachers don't know. This cannot stand alone: it has to follow a noun phrase (in this case things) which it modifies. In effect, it acts as an "adjective". As FumbleFingers points out, if you said the things here it would be equivalent to your first sentence; but the version without the the says that there are merely some things which he knows but other teachers don't:

He knows some things which other teachers don't know.

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  • You don't seem to have mentioned it, but to me, that or which is effectively optional in this context. I find it interesting that, as you say, in the "bound relative clause" version, things inevitably implies some, but not all things. But if it's the things, that implies everything to me. So I've been treating my moribund kundabuffer with the only beer that "grammatically" should help, but I think those adverts are lies - it still ain't working properly! – FumbleFingers Reinstate Monica Sep 17 '13 at 14:32
  • @FumbleFingers I did mention the which/that option. But your point about the is spot on -- fixed. As for advertising, that's highly-compensated abuse of language. – StoneyB on hiatus Sep 17 '13 at 14:40
1

The two have very different interpretations, both make grammatical sense.

  • "He knows what other teachers don't" means "He possesses knowledge that other teachers don't have".
  • "He knows that other teachers don't" means "He is aware that other teackers don't (do something)".
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  • 2
    I think not: OP's second sentence is "He knows things that other teachers don't". – StoneyB on hiatus Sep 17 '13 at 13:57

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