September 2005 Vol. 10 Issue 3
Grammar Trap: that vs. which

Which word should I use? That is the dilemma facing us today.

What is the proper use of "that" and "which"?

According to most grammar guides:

  • Use "that" in essential (or restrictive) clauses.
  • Use "which" in unessential (or nonrestrictive) clauses.

OK, what does that mean

A nonrestrictive clause is like a parenthetical remark or an aside. Removing a nonrestrictive clause doesn't fundamentally alter the sentence's overall meaning.

A restrictive clause limits or defines what is being talked about. Without such clauses the overall meaning of the sentence is lost. Very often, restrictive clauses don't require "that" at all.

So what is and isn't essential to meaning? The answer to this question is what makes this such a thorny issue: it depends on what the writer or editor wants the sentence to mean.

Example: The pasta sauce, which came from Buttergut Kitchens, was a crowd favorite.

Here, the fact that the sauce came from Buttergut Kitchens is merely extra information (it's unessential/nonrestrictive), so "which" is used. The most important message of this sentence is that the sauce was a crowd favorite. Where the sauce came from is of secondary importance, so it's parenthetical and offset by commas.

Example: The pasta sauce that came from Buttergut Kitchens was a crowd favorite.

Here, the fact that the sauce came from Buttergut Kitchens is important information (it's essential/restrictive), so "that" is used. The key message of this sentence is that it was the sauce from Buttergut Kitchens (and not any other sauce) that the crowd enjoyed.

Of course, there is an exception to this rule. When you're referring to a person, (almost) always use "who" instead of "that" or "which" (See the Grammar Trap, "That vs. Who").

Example: Kat Clinger, who is the proprietor of Buttergut Kitchens, was pleased with the response (unessential/nonrestrictive).

Example: The one who was most pleased was Kat Clinger, proprietor of Buttergut Kitchens (essential/restrictive).

So when you're forced with a choice between "that" or "which," ask yourself: "How important is this information?"

Kevin Leigh Smith, kevlsmith@purdue.edu

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