That vs. which

Brits use the two interchangeably. North Americans use "that."

I don't. I use "that" for restrictive clauses, and "which" for nonrestrictive, just like I was taught in school 50 years ago. However, you are right, many use them interchangeably. Using "which" to introduce a restrictive clause is not strictly incorrect in American English, but it is generally avoided, especially in formal writing.

You could argue that the "which for nonrestrictive, that for restrictive" rule is in fact a 'pseudo rule'. Geoffrey Pullum, co-author of the Cambridge Grammar of the English Language, says the restriction “has no basis”. "Which" can be used with restrictive clauses. Jane Austen did so, as did Dickens, Melville, Stoker, and countless good writers. It’s in the King James Bible [“Render unto Caesar the things which are Caesar’s, and unto God the things that are God’s”]. Non-restrictive "that" appears in Macbeth.

The Columbia Guide to Standard American English says: "most of us use which almost interchangeably with that in restrictive modifiers and rarely but sometimes use that to introduce nonrestrictive modifiers. . . . Best advice: use that or which or nothing, depending on what your ear tells you. Then, when writing for certain publications, know that you may have to replace a good many whiches with thats, and perhaps a that or two with a which, to conform to the “rule” almost no one follows perfectly in other than Edited English and few can follow perfectly even there."

If they are both correct, is there any difference in meaning between the following sentences?

1) I ate the pie that made me happy.

2) I ate the pie, which made me happy.

Thank you.

They are "correct", in the sense that they are grammatical, but they do not mean the same thing. In this example "which" and "that" cannot be interchanged. Note the comma which introduces the non-restrictive clause "which made me happy".

1 means "I ate the particular pie which had previously (somehow) made me happy."

2 means "I was made happy by eating the pie."

Yes, there is a difference, mainly because one lacks a conjunction or offsetting comma. As it stands, (1) seems to say that it is the pie itself (not the eating) which makes you happy, while (2) specifies the source of the pleasure. To me, they would basically be the same with one slight change:

1) I ate the pie and that made me happy.

2) I ate the pie, which made me happy.

I don't know why Layman got a thumb down for his correct reply. I have rectified that.

Thank you.

Thank you.

Old Groucho Marx joke:

A: I shot an elephant in my pajamas this morning.

B: What was he doing in your pajamas?

With that in mind, I suppose you could argue that even this construction is ambiguous:

"2) I ate the pie, which made me happy."

The question can still be asked: What made you happy, the pie, or eating it?

Generally, "which"clauses can be taken out of the sentence and the meaning does not change. Off-set it with commas.

"That" clauses tend to be important to what is being meant.

The car that was brand new broke down.

The car, which was brand new when I bought it, broke down.