Lesson Transcript

Hi, everybody. My name is Alisha. Today, I'm going to talk about the difference between "which" and
"that." "Which" and "that" are both relative pronouns, but a lot of people confuse the two. So, let's talk about how to use them.
First, a quick overview. Which. First, we use "which" in what are called non-restrictive relative clauses. We use "that," on the other hand, in restrictive relative clauses.
Before we continue, let's talk about the difference between non-restrictive clauses and restrictive clauses. The difference here, a non-restrictive clause, first of all, where we use "which" is a clause that does not have information essential to understanding the noun it is connected to. I'll show you some examples in just a minute. A restrictive clause, however, is a clause that has information essential to our understanding of that noun. We need the information in the restrictive clause to completely understand the noun or the noun phrase it is attached to. A non-restrictive clause is extra information. We don't need the information to understand the noun or the noun phrase, it just provides some more information.
Let's take a look at a few examples of this. The first example I have is rather extreme, but it's just to show the differences between these two. First, "The school that I parked my car next to is dangerous." Here, my noun is "school." Here, I've got the relative pronoun "that." I have "The school that I parked my car next to is dangerous." I've used "that" here because my clause is a restrictive clause. I need this information. "The school that I parked my car next to is dangerous." If I remove this, "The school is dangerous," the sentence is correct, however, the meaning changes. The key here is "that I parked my car there." I want to explain that specifically, "The school that I parked my car next to," this school in particular, is dangerous. "That" shows us that it's a restrictive clause. We have to use that in this sentence because the information is essential to our understanding.
In this sentence, however, "The school which has a tennis court is dangerous," I've used "which." "Which" is a non-restrictive, is used in non-restrictive clauses. This shows us it is extra information. The school has a tennis court. Do I need to know this information? No. It's just extra information. If I remove this clause, "the school is dangerous," the root sentence, the basic sentence, stays the same. This is just extra information. It doesn't necessarily tell us essential information about the situation. So, we use "which" to show that. It's a non-restrictive relative clause.
As I said, this is a rather extreme example, so let's take a look at something that's a little bit more complex. Let's look at the next two sentences. First, "The car, which I bought last year, is already having trouble." And, "The car that I bought last year is already having trouble." These are very similar sounding sentences, however, our choice of "which" or "that," as well as the commas, which I'll talk about later, have changed the meaning. There are a couple of key differences here.
One, by seeing in the first sentence that we're using a non-restrictive clause here with "which," we see "the car which I bought last year." This shows us that this is extra information about the car. Here, however, we see that this is essential information. "The car that I bought last year is already having trouble." The speaker could be saying here with this sentence, the second sentence, "The car that I bought last year," specifically a car that the speaker purchased the previous year. This sentence means, therefore, the speaker might have other cars. The speaker is specifically meaning this specific car that he or she bought last year. In this sentence, with the non-restrictive clause, we don't have the same nuance. "The car which I bought last year" is just extra information in this sentence. Here, "The car that I bought last year," this is indicating a specific car. This one, with the non-restrictive clause, it's just giving us extra information. The speaker may or may not have another car. We don't know. That's all I want to say about that.
But a question that many people have is how do you know whether it's a restrictive or a non-restrictive clause? This is a quick tip, a quick hint, for native speakers and non-native speakers, actually. Is it restrictive, non-restrictive? How do I know? To do that, remove the clause. Just take the clause out of the sentence. Is the meaning of the sentence the same? Is the sentence still grammatically correct? Is it okay? If yes, if the sentence is okay, the meaning is the same, it's a non-restrictive clause. If no, if the meaning changes, if you lose some key information, it is a restrictive clause. This is a quick hint if you're not sure whether to use "which" or whether to use "that," try this test, this quick test. Just take it out and see if the meaning changes.
The last thing I want to talk about here is the use of commas. You'll notice I used commas throughout this lesson, and also when I was reading, they create a natural pause around this extra information, but when do you use them? We should use commas around non-restrictive clauses. You can see, I used them here and here in the example sentences. We use commas around non-restrictive clauses only. Again, "This lesson, which is being recorded, is about 'which' and 'that.'" When you're reading, it creates a natural pause so the reader knows there's going to be extra information there. The reader can understand through use of these commas.
However, do not use commas around restrictive clauses. For example, "The lesson that I just taught was about how to use 'which' and 'that.'" This is a restrictive clause. I mean, specifically, this lesson that I just taught was about how to use "which" and "that." I should not include commas here because I'm not including any extra information. All of the information is essential. It's the same with all of the other example sentences I used in this lesson. There are no commas included because all of the information is essential. The reader needs to understand everything in one piece. You can think of it that way.
That's an overview of the differences between "which" and "that," restrictive clauses as well and a couple of comma tips too. I hope that this was a useful lesson for you. If you have any questions, of course, please feel free to let us know in the comments. Thanks very much for watching. I will see you again soon. Bye-bye!

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