The fact which(that) I told you is not true.

[keannu]

Just to check out a workbook mistake, in this example, both which and that can work, right?

ex)The fact which(that) I told you is not true.

[SirGod]

* Not a teacher

I think that is a better option than which in this particular case, but both would work.

[Tdol]

They both work for me, but as it's not true, is it a fact? What I told you is not true would work better for me.

[BobSmith]

I've always considered fact to be the opposite of opinion, but not always true. As in:

5 : a piece of information presented as having objective reality (emphasis mine)

You might hear, "I don't believe you; get your facts straight." Here the "facts" are suspect, but they're still facts.

[emsr2d2]

Just to check out a workbook mistake, in this example, both which and that can work, right?

ex)The fact which(that) I told you is not true.

I agree with Tdol that if it isn't true, it's not a fact. However, if you had told someone something earlier in the day which you had claimed was a fact and you were now going back to them to tell them that you had discovered that you were wrong, you might say "Sorry, the "fact" ... is not true" or "Sorry, that "fact" has turned out not to be a fact!"

My personal opinion is that you need neither "that" nor "which".

The thing I told you is not true.

[Tdol]

I've always considered fact to be the opposite of opinion, but not always true. As in:

5 : a piece of information presented as having objective reality (emphasis mine)

You might hear, "I don't believe you; get your facts straight." Here the "facts" are suspect, but they're still facts.

But The fact I told you isn't true doesn't work for me. You could say What I said was a fact wasn't true, but without saying something like this, the sentence is a mess to me because it contradicts itself if it uses the word fact.

[BobSmith]

it contradicts itself if it uses the word fact.

Yes, unless it's is defined as I stated.