Which vs. That

[Ispeakgood]

What is the rule behind when to use the word "that" versus the word "which"?

For example...

"All the animals in the barn, which burned down last night, survived because they were sleeping in the fields"
or
"All the animals in the barn, that burned down last night, survived because they were sleeping in the fields."

This may be a bad example, but it was the best I could think up...



Thank you,
Scott Stephens

[Tdol]

Don't use 'that' after a comma:

The United States, which is the world's richest nation,.... (Here, because there is a comma, I'm just giving extra information, not defining which United States- I couldn't use 'that' here). Your example is ambiguous. If there was only one barn, then you'd have a comma and 'which' because you'd be telling me more about the barn. If there were a number of barns, then you'd be defining the barn, so there would be no comma and you could use 'that' or 'which' in British English. I believe the tendency in American English is to use 'that' in the second case and 'which' in the first.

[mykwyner]

The key to knowing which relative pronoun to use in American English is whether or not the clause gives information that is essential to the meaning of the sentence. If the information is essential (there are many barns, and we're talking about the one that burned) then we call it a restrictive or bound relative clause and we introduce it with that and don't use commas. If the information is non-essential (there is only one barn, and everyone knows it burned) then it is non-restrictive or unbound and is introduced with which and enclosed in commas. Think of the non-restrictive relative clause as parenthetical and the commas acting as parentheses.

[Casiopea]

Additionally, if you delete the clause and the meaning stays the same, then the clause is added information. If it's added information, use a comma to separate the clause from the rest of the sentence. For example,

All the animals in the barn survived because they were sleeping in the fields.

Question: What did the animals survive? Ah, yes, the burning of the barn. So, the clause "that burned down last night" is important, which means no commas are required:

All the animals in the barn that burned down last night survived because they were sleeping in the fields.

Know your audience. Even in American English writers will use 'which' without a comma. And know the terminology. The terms defining clause and non-defining clause are also used today. A defining clause defines or tells us more about the noun it modifies:

Defining: . . . the barn that burned down last night . . . .
Defining: . . . the barn which burned down last night . . . .
Non-defining: . . . the barn, which burned down last night, . . . .