Let’s get something straight at the very beginning–when I write about grammar, I’m talking about the written word, not the spoken. Spoken language and written language are, whether the most prescriptive of us alive can stand it or not, two different things. It is my opinion that the written word needs to follow grammar rules the spoken word can let slide. Let us also get straight that American English and British English are also two different beasts. I am fully aware that the Brits use that and which pretty much interchangeably, even though their basic grammar on the matter is the same, and they prefer which, while Americans overuse that (before a verb, ie: She knew THAT she had to go home, rather than, She knew she had to go home.) The Brits also love the past imperfect at the moment–a huge no-no for American writers–but that’s a horse of a different color, and changes with the tide.
I’ve written on this subject before, and I admit to gakking past posts to write this one, but that and which apparently and continously remain a challenge to writers everywhere–and I don’t mean those of us who write professionally. The internet reminds me of this on a daily basis. It is one of my pet peeves, and something I am a stickler about seeking out and destroying.
THAT is used with a restrictive clause, part of a sentence you can’t get rid of without changing the meaning, because it restricts some other part of the sentence. For example:
Mice that don’t like cheese will never fit in with mouse society.
It doesn’t matter whether or not this statement is true; what does matter is the that don’t like cheese cannot be taken out of the sentence without losing the meaning. It’s a restrictive clause. Without that clause, the sentence says that no mice will ever fit into mouse society. With the clause, it’s only those unfavorably disposed to cheese that won’t.
WHICH is used within a non-restrictive clause, part of a sentence that can be left out–not which can be left out–without changing the meaning. Non-restrictive clauses require a comma, or commas. It’s an easy indicator. Restrictive clauses don’t usually require commas.
The building, which stood on the corner of 1st and Grandview, was demolished during the Great Mouse Rebellion.
Which stood on the corner of 1st and Grandview is the non-restrictive clause. It is an added bit of information that can be removed without actually changing the meaning of the sentence. The building is demolished during the Great Mouse Rebellion. The clause is an aside, a bit of information that, while clarifying, isn’t necessary. And there is your biggest clue–if you can take out the clause without changing the general meaning of the sentence, use which.
The above is an example of a non-restrictive clause plonked down in the middle of a sentence. The ones tagged on to the end get a little trickier.
The building was demolished during the Great Mouse Rebellion, which was an unhappy event for anyone.
The building was demolished during the Great Mouse Rebellion that was an unhappy event for anyone.
Can you see the subtle–and some will say, totally irrelevant–difference? With the comma + which, the above sentence says that the destruction of the building was the unhappy event, while the second–taking out the comma and replacing which with that–it says that the Great Mouse Rebellion was the unhappy event.*
Does it matter? To some it won’t. To some, it will. There nevertheless is a difference in meaning. And that brings me to my last and, for me, most important point–that tends to be a filler word, a word we lean on when connecting thought to image, image to thought. I don’t like filler words, even though I overuse that like a champion. It is invisible to me while writing first draft, and the first search I do when starting revisions. Which is almost always an aside, and thus, telly. Not only is it telly, it’s author intrusion. You’re waving a flag for your reader, pulling them out of the action to give them information better given another way.
Like adverbs, that and which are necessary. They’re beneficial. They can do the job when called for; just be aware of how often you do the calling.
(*And before you argue that the first sentence could say both, in fact, it can’t. The building being destroyed is the event–during the Great Mouse Rebellion is a prep-phrase modifier. The clause goes to the former, not the latter. It’s like knowing 5 + 5 x 5 + 5 = 35. You have to know what goes with what–and that is what commas and such are for!)