A message from a reader prompts this post about “that” and “which.” I was already earning a living as a journalist before I finally understood how to use “that” and “which” properly, so I certainly understand the confusion. This tricky choice seems to give a lot of writers (and their editors) trouble.
In a nutshell, if the information that follows “that” or “which” is limiting or key to understanding the sentence, you need “that.” If the information is extra and not limiting then use “which.” (In grammar speak, “that” introduces essential or restrictive clauses, and “which” introduces nonessential or nonrestrictive clauses.)
Here are sentences that illustrate (I hope):
The house that belongs to the Johnsons stands at the corner of Maple and Elm streets.
The large, white house with gables, which belongs to the Johnsons, stands at the corner of Maple and Elm streets.
In the first sentence, we mean to tell the reader that the house we are writing about is the one that belongs to the Johnsons (not to the Smiths or the Browns). We consider the information essential and limiting. You can’t understand what house we’re talking about without the clause.
In the second sentence, we are giving extra information. We have already described the house (large, white and with gables) and, oh, by the way, it also happens to belong to the Johnsons. In “Working With Words,” a handbook for writers and editors (fourth edition, Bedford/St. Martins, 2000), the writers advise thinking of a nonessential clause as an aside — a little something extra.
You’ll also notice in the example sentences above that we use commas to set off “which” clauses. That is true of any nonessential clause. On the other hand, don’t use commas to separate essential clauses that begin with “that.”
Here is another pair of examples:
The grammar book that I checked out of the library in Hickory is 27 years overdue. (I mean only the grammar book that I checked out of the library. The clause “that I checked out …” is essential.)
This grammar book, which I bought at a bookstore in Columbia, has proved invaluable. (I am adding, oh, by the way, I bought this book in Columbia. The clause is an aside.)
Witnesses saw a car that had a broken taillight driving away from the scene of the attack. (Not a car with a smashed headlight or one with the dented passenger door.)
Witnesses saw a blue 1958 Edsel, which has a broken taillight, driving away from the scene of the attack. (Oh, and by the way, the car has broken taillight.)
This is a quick lesson in “that” and “which.” You will encounter more complex instances, but I’ll save those for another post.
This article was originally posted by the Raleigh News & Observer, a subsidiary of The McClatchy Co.; is posted here to provide continuity; and is copyright © 2011 The News & Observer Publishing Company, which reserves the right to remove this post.