The difference between x and y is that x is produced by z.
The difference between x and y is the fact that x is produced by z.
That x is produced by z is the difference between x and y.
The fact that x is produced by z is the difference between x and y.
I am wondering if they mean the same thing. If they are not, please tell me the difference.
I am wondering if always the phrase the fact exists in deep structures of the sentences as above.
Best Answer
Yes, they all mean the same thing. Yes, you could read "that" as meaning "the fact that". It is more common to leave "the fact" out, except for emphasis. Both #3 and #4 are grammatically correct, but awkward; #1 and #2 would be considered to be more straightforward.