Answer: When is it appropriate to use "which" vs. "that"?
t_verano poses an interesting question: When is it appropriate to use "which" vs. "that"? What is the appropriate comma use in each situation?
Is there, in fact, a distinct rule that applies to this situation? Or does it depend entirely on mood, which can change from one moment to the next?
Let's find out, with examples from Discworld...
There is a distinct difference between the times when you should use "that" and the times when you should use "which".
To quote Fowler in Modern English Usage:
... if writers would agree to regard that as the defining relative pronoun and which as the non-defining, there would be much gain both in lucidity and in ease.
Which is wonderfully informative and not confusing in the slightest... Luckily, we can boil it down to something much, much simpler with the help of a couple of examples. Let's take a sentence at random. Say... The cabbages that grew freely on the plains of Sto Lat had become a staple diet for the Watch.
Now watch it change ever so slightly: Cabbages, which grew freely on the plains of Sto Lat, had become a staple diet for the Watch.
There are slight differences between these two sentences. In the first, the fact that the cabbages come from Sto Lat seems to be vital; in the second, it's merely an interesting detail coming along for the ride. When we have a detail that is vital to the sentence, indeed without which the sentence may make no sense, then we use "that". On the other hand, when we have an interesting detail that enhances a sentence but is not strictly necessary, we use "which".
It's important to note that a comma always precedes a clause starting with "which". This re-inforces the fact that we're introducing a little detour, rather than continuing straight ahead with the sentence.
Let's have a look some more examples, just for fun.
Angua was sure Carrot secretly liked the blue collar that she wore more often than any other.
vs.
Angua was sure Carrot secretly liked the blue collar, which she wore more often than any other.
If we look more closely at the example using "that", it's possible to see that the meaning is still clear, even if we remove it.
Angua was sure Carrot secretly liked the blue collar she wore more often than any other.
In many instances, "that" isn't actually necessary and is actually implied by the meaning or the phrasing of the sentence in question. Occasionally, as in this case, a sentence will actually flow more smoothly if the "that" is removed.
Carrying on with further examples:
Cheery swallowed bravely and took down the giant axe that hung on one wall of her office (mostly for decoration).
OR
Sergeant Colon's carefully expressionless face nevertheless managed to loudly broadcast his disbelief that a book, which contained an unfortunate dearth of helpful woodcuts, could possibly help anyone to learn how to solve crime.
So whenever you're faced with a decision between "that" and "which", just ask yourself how vital the particular piece of information is. Can the sentence exist without it, even though it adds fascinating detail? If so, grace it with a "which" and a comma. Is it a vital piece of information that absolutely, positively has to be there? Then it requires a "that".
Is there, in fact, a distinct rule that applies to this situation? Or does it depend entirely on mood, which can change from one moment to the next?
Let's find out, with examples from Discworld...
There is a distinct difference between the times when you should use "that" and the times when you should use "which".
To quote Fowler in Modern English Usage:
... if writers would agree to regard that as the defining relative pronoun and which as the non-defining, there would be much gain both in lucidity and in ease.
Which is wonderfully informative and not confusing in the slightest... Luckily, we can boil it down to something much, much simpler with the help of a couple of examples. Let's take a sentence at random. Say... The cabbages that grew freely on the plains of Sto Lat had become a staple diet for the Watch.
Now watch it change ever so slightly: Cabbages, which grew freely on the plains of Sto Lat, had become a staple diet for the Watch.
There are slight differences between these two sentences. In the first, the fact that the cabbages come from Sto Lat seems to be vital; in the second, it's merely an interesting detail coming along for the ride. When we have a detail that is vital to the sentence, indeed without which the sentence may make no sense, then we use "that". On the other hand, when we have an interesting detail that enhances a sentence but is not strictly necessary, we use "which".
It's important to note that a comma always precedes a clause starting with "which". This re-inforces the fact that we're introducing a little detour, rather than continuing straight ahead with the sentence.
Let's have a look some more examples, just for fun.
Angua was sure Carrot secretly liked the blue collar that she wore more often than any other.
vs.
Angua was sure Carrot secretly liked the blue collar, which she wore more often than any other.
If we look more closely at the example using "that", it's possible to see that the meaning is still clear, even if we remove it.
Angua was sure Carrot secretly liked the blue collar she wore more often than any other.
In many instances, "that" isn't actually necessary and is actually implied by the meaning or the phrasing of the sentence in question. Occasionally, as in this case, a sentence will actually flow more smoothly if the "that" is removed.
Carrying on with further examples:
Cheery swallowed bravely and took down the giant axe that hung on one wall of her office (mostly for decoration).
OR
Sergeant Colon's carefully expressionless face nevertheless managed to loudly broadcast his disbelief that a book, which contained an unfortunate dearth of helpful woodcuts, could possibly help anyone to learn how to solve crime.
So whenever you're faced with a decision between "that" and "which", just ask yourself how vital the particular piece of information is. Can the sentence exist without it, even though it adds fascinating detail? If so, grace it with a "which" and a comma. Is it a vital piece of information that absolutely, positively has to be there? Then it requires a "that".