When to Use Which and that in English

Many students (and native English speakers!) may not know exactly when to use which and that in English. The difference between the two words can seem too negligible to really matter- and a lot of grammar books will tell you that there is no difference. So why not use them both interchangeably, right?

Wrong.

Believe it or not, there really is a method to the madness (reason why). There is a very specific reason to use which and that in English, and it all depends on the information you want to provide.

The Difference Between Which and That in English

One of our favorite grammar blogs, Grammar Girl, describes it like this: “if removing the words that follow [the which or that] would change the meaning of the sentence, use “that.” Otherwise, “which is fine.”

Some argue that the rules are much more complicated than this, but this is the easiest way to think about it.

Restrictive or Defining Clauses

This rule has to do with what is called a restrictive or  defining clause. A restrictive clause is a part of a sentence that cannot be removed, as doing so will change the meaning of the sentence. You need this information to more clearly “define” exactly what is meant.

For example, if you say, “Dogs that bite are scary,” “that bite” is the restrictive clause. If you took “that bite” out of the sentence, you would be saying that you are afraid of all dogs. However, you are just afraid of the dogs that bite.

See the difference?

When there is a restrictive clause in a sentence, use the word “that.” This will help indicate which information is necessary for your sentence to be understood. It more clearly specifies exactly what kind of dogs you are afraid of.

Non-Restrictive / Non-Defining Clauses

A non-restrictive or a non-defining clause is the exact opposite of a restrictive clause. A non-restrictive clause is extra information that when taken out of a sentence, the main point of the sentence won’t change. Think of a non-restrictive clause as just adding information that the listener or reader might like to know, but doesn’t need to know.

For example, “Diamonds, which are just made of carbon, are really expensive.”

In this sentence, your main goal is to communicate that “Diamonds are really expensive.” If you take out the non-restrictive clause, “which are just made of carbon”, you’ll still perfectly communicate this sentiment (idea, concept). The phrase, “which are just made of carbon” only stands to provide extra information about diamonds… and perhaps to explain why you find them to be overpriced!

When there is a non-restrictive clause in a sentence, use the word “which“.

Pro-tip: you should also have commas around a non-restrictive clause, whereas there are no commas around a restrictive clause.

Exercises: When to Use Which and That in English

Ready to try a few exercises? Add “which” or “that” in the blanks. Good luck!

  1. Flowers, __________ are overpriced in my opinion, look nice on a dinner table.
  2. The book __________ I gave to my mother is almost 10 years old.
  3. When we go on vacation, __________ only happens once a year, we always go to the sea.
  4. I really don’t like Christmas cakes __________ have dried fruit in them.
  5. The iPhone, __________ first came out in 2007, is very popular among young people.
  6. Who threw the ball __________ broke the window?
  7. The sale, __________ only lasted one day, was advertised on TV for weeks!

Answers: 1. which 2. that 3.which 4. that 5. which 6.that 7. which

If you’re curious about a few more common confusions, check out our blogs on Affect vs EffectIts vs It’sAmerican vs UK spelling.

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All in all, the difference between that and which in English is not as tricky as it may seem! Why not try out a few of your own examples of sentences with restrictive and/or non-restrictive clauses in the comments, and we’ll give you any help you may need.

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Erin Duffin lives in Hamburg, is an English teacher,  yoga instructor, and likes to write about topics that are helpful, fun, and interesting, which should be obvious!  

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