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By Don Hauptman
A frequent usage problem is confusion about the distinction between that and which. Indeed, I sometimes find myself pondering the right choice in a specific context. In such cases, I consult a file of articles on the subject that – or is it which? – I’ve clipped and saved over several decades.
The rules may appear to be a bit complicated. But once you know them, your ear, or eye, will usually give you the right answer. Here are the guidelines:
Use that to introduce a restrictive clause – one that identifies, defines, or limits what’s in that clause, making the information essential to the meaning of the sentence. Use which to introduce a nonrestrictive clause – one where the information is incidental and could be omitted from the sentence without changing its meaning.
Is the above explanation sufficiently puzzling? An illustration should make things clearer. The following sentences are correct:
- This is the marketing plan that Tom wrote.
- This marketing plan, which Tom wrote, is due on Friday.
The first example is restrictive. It defines or limits all possible marketing plans to the one written by Tom. So that is the right word. In the second example, the reference is nonrestrictive. If the clause “which Tom wrote” were omitted, the sentence would still make sense and its basic meaning would be unchanged.
Note also that the clause “which Tom wrote” is set off by commas. If a clause is, or can be, framed with a set of commas – or parentheses or dashes – the information is most likely optional and which is correct.
Although some unusual that/which dilemmas can arise, the most common error is to say or write which when that is correct. By applying the above guidelines, you can avoid or eliminate such incorrect uses of which. One rule of thumb I use: If that sounds correct, it’s probably the right choice.
Some language authorities consider this issue to be arbitrary or unimportant, while others advocate observing the rules. I’m in the latter camp. The proper word can make one’s writing clearer. Indeed, situations exist where that instead of which, or vice versa, can create ambiguity or totally change the meaning of a sentence. So the distinction is worth preserving.
[Ed Note: For more than three decades, Don Hauptman was an award-winning independent direct-response copywriter and creative consultant. He is author of The Versatile Freelancer, an e-book recently published by AWAI that shows writers and other creative professionals how to diversify their careers into speaking, consulting, training, and critiquing.]