That vs. Which

Today's topic: That vs. Which

"Should I use 'that' or 'which' in this sentence?"  It's a frequently asked question, and a frequent blunder.  Fortunately, the rules governing "that" and "which" are fairly simple.  Let's clear up this troublesome topic, shall we?

THAT:

"That" should precede a restrictive clause.  What's a restrictive clause?  It's a phrase that is essential to the meaning of a sentence.  If you eliminate a restrictive clause, the meaning changes.  Let's look at some examples.

Cupcakes that have caramel in them are addictive to me.

If we remove the underlined clause, we totally change the meaning.  I'm not addicted to regular cupcakes, just the ones with caramel in them. 

Flowers that have a strong scent fascinate my dog. 

Not all flowers have a strong scent, so if we remove the underlined clause we totally change the meaning of the sentence.  My dog isn't fascinated by odorless flowers.

The enchiladas that were made with hot peppers made him sick.   

By now, you get the idea.  The regular enchiladas didn't make him sick, only the ones with hot peppers.

WHICH:

Use "which" before a nonrestrictive clause.  What is a nonrestrictive clause?  It's a phrase that can be omitted from a sentence without substantially changing its meaning.  Nonrestrictive clauses are non-essential; they  just provide extra details.  Let's look at some examples.

The Ferrari Enzo, which costs a fortune, is my brother's dream car.

If we eliminated the underlined phrase, it wouldn't substantially change the meaning of the sentence (everyone knows Ferraris are expensive). 

The couch, which has a wine stain on the left armrest, needs to be cleaned.

Again, the message is the same with or without the underlined portion.  The couch needs cleaning.  The underlined clause simply gives us more information about why.

Notice that the nonrestricted clauses in the two examples above are bookended by commas.  In fact, nonrestricted clauses are almost always either surrounded by commas or preceded by them (as in "We saw a double rainbow, which was gorgeous").

If you have trouble remembering phrases like "restricted clause" and "nonrestricted clause," just remember this: If you could take out the phrase without substantially changing the meaning of the sentence, use "which."  If you need the phrase to make your meaning clear, use "that."

One more tip:  Never use "which" or "that" when referring to people; use "who" or "whom."  Example:  The participants, who were chosen through random sampling, ranged in age from 18 to 35.

Pretty simple, no?  I hope you've found this week's post helpful.  As always, happy scribbling!