Which vs That

When teaching relative clauses there are two hard parts. Defining vs Non-Defining clauses and the differences between who, whom and whose.

Who vs Whom has gotten some popularity in Internet memes, but which vs that still has not been given as much attention. I predict within the next 10 years people will start insulting people for using it incorrectly in YouTube comments.

In order to understand the difference between which and that you need to understand the essentials of comma usage with relative clauses, in short the difference between defining(essential) and non-defining (non-essential) clauses.

When I teach I tell students to think of commas as balloons. When something is surrounded by commas that information can “fly away” since the balloons tell you it isn't necessary.

My boyfriend, who is a teacher, is sexy.

The information in the commas is non-defining. We already know who my boyfriend is we don't need to know that he is a teacher. Thus: “My boyfriend is sexy” has the same essential meaning.

My boyfriend who is a teacher is sexy.

Without the commas, “who is a teacher” becomes defining or essential information. This means the information is needed or we don't know who I am talking about. It suggests I have more than one boyfriend and the one who is a teacher is sexy (perhaps the engineer whom I am also dating is not sexy).

So let's try it with another sentence.

My friend, who lives in Paris, is speaks French.

How many friends do I have based on that sentence? Just one, or more?

Since there are commas, it is extra information. Consequently the sentence suggests I only have one friend.

 
My friend who lives in Paris is speaks French.

On the other hand this sentence has no commas. This suggests that the relative clause is necessary thus I have more than one friend.

Got it? Let's check. Select the correct sentence:

My cat who is my only pet is annoying. OR
My cat, who is my only pet, is annoying. (yes I use who with pets).

Since I only have one cat the relative clause is not needed and thus should be in commas: My cat, who is my only pet, is annoying.

How does this apply to which and that?

Which is ONLY used with extra information clauses, whereas that is ONLY used with defining clauses.

For example.

News that is controlled by the rich is biased.

This sentence requires the relative clause, hence it suggests that some news is not controlled by rich people and only news controlled by rich people is biased.

News, which is controlled by the rich, is biased.

Conversely, in this sentence the relative clauses is unneeded and the sentence could be re-written as, “News is biased,” thus it suggests that all news is biased.

Starbucks that is near the park has the cutest employee.

There are many Starbucks in the city and this sentence is talking about the one specific Starbucks found near the park.

Starbucks, which is near the park, has the cutest employee.

There is only one Starbucks (weird, but that's true in some cases) and it has the cutest employee.

The last difference is easy. Which is ONLY used with objects. That is used with objects and people.

To recap

Which is ALWAYS used with commas and objects.

That is ALWAYS used without commas for objects and people.

So try it out:

A. My television, which is the only one I have, is broken

B. My television that is the only one I have is broken.

C. My television which is the only one I have is broken.

D. My television, that is the only one I have, is broken.

I only have one TV, so the relative clause should be in commas (so it is A or D) and since we never use that with commas the correct answer is A.

Again!

A. Justin Bieber's album, which was his debut album, sold tons of copies.

B. Justin Bieber's album that was his debut album sold tons of copies.

C. Justin Bieber's album which was his debut album sold tons of copies.

D. Justin Bieber's album, that was his debut album, sold tons of copies.

Justin Bieber has had more than one album. So the relative clause is needed, otherwise we aren't sure which album they are talking about. As a result, we can say the correct sentence has no commas and is either B or C. Since we ALWAYS use commas with which the answer is B.

Once more!
A.Tyra Banks' TV show, which isn't cancelled, is my reality TV addiction.

B. Tyra Banks' TV show, that isn't cancelled, is my reality TV addiction.

C. Tyra Banks' TV show which isn't cancelled is my reality TV addiction.

D. Tyra Banks' TV show that isn't cancelled is my reality TV addiction.

Tyra used to have a talk show. Now, she just has a modeling show. Since there is more than one Tyra television show, we need the relative clause. Consequently, our answer can't have commas and has to use that. That means the answer is D.

Hope that helps! Do you have any special activities you do when you are talking about defining vs non-defining clauses? I tend to just try to make my students practice with a lot of worksheets that I make as interesting as I can with celebrities, current movies, crazy examples etc.

Like You're vs Your Flyswatter is a great game for reviewing this. I also like finding weird news articles and making them combine the sentences using which or that.

How do you get students to practice definind vs non-defining phrases?