Meet Our Academic Team: That vs. Which

Kaplan Teacher

06 January, 2017

Welcome back to our Kaplan Teacher lesson series. This week’s grammar post is brought to you by Mary Voorhees, a teacher at Kaplan English school in Seattle. Mary has been teaching for over 6 years and working with Kaplan for 4.

"I like teaching English to international students because the students are so funny and interesting. English is an international language. If you can speak English, you can speak to many people in the world."

THAT VS. WHICH

So what’s the difference between that and which? Both these words are used when we form relative clauses. A relative clause is part of a sentence that gives more information about a noun (people and things) and usually starts with relative pronouns like who, which, and that. They can often be understood as the combination of two sentences. Here are some examples:

> I like dogs that are cute.

> My dog, which is the cutest dog, is my favorite.

But when do we use that and when do we use which?

First, it helps to know the rules:

Use that in identifying clauses – these tell us which one and do not have commas
Use which in non-identifying clauses – these give us extra information and are separated from the rest of the sentence with commas

What are identifying and non-identifying relative clauses?

There are two types of relative clauses: identifying and non-identifying. An identifying relative clause answers the question: which one? It identifies exactly what I’m talking about. Look at the relative clause examples below and try to guess which example is identifying.

A. I like dogs. Dogs are cute. I like dogs that are cute.

B. My dog is my favorite. My dog is the cutest dog. My dog, which is the cutest dog, is my favorite.

If you guessed A, you’re right! Which dogs do I like? Dogs that are cute. In example B, we know we are talking about my dog, so the information, “which is the cutest dog” doesn’t tell us which dog. It’s not identifying; it’s just extra information about my dog.

Now guess which of these 2 examples is identifying:

A. My parents’ house, which is small, brings back a lot of memories.

B. There are two houses in the woods. The one that is by the lake is smaller than the other one.

If you guessed that B is identifying, you’re right! There are two cabins. The phrase, “that is by the lake” tell us which cabin is smaller. The information about my parents’ house is just extra.

Another way to understand this is that if there is only one of something (a single object), the clause is almost always non-identifying. Here are some examples:

> I love Pokémon Go, which is always open on my phone.

> The Statue of Liberty, which was given to us by France, is green.

> I live in Seattle, which is the best city in the US.

Because there is only one Seattle, one Pokémon Go, and one Statue of Liberty, we don’t need the extra information to identify which one we’re talking about. Compare the sentences above to these examples:

> I like games that help me to get exercise.

> I visited the statue that is green and was given to us by France.

> I live in a city that is very rainy.

These relative clauses tell us which games I like, which statue I visited, and which city I live in.

Helpful hint: You might also notice that non-identifying clauses always have commas and identifying clauses do not have commas. Keep that in mind when deciding to use that or which.