Which vs. That: What’s the Difference?

If you aren’t sure when to use which vs. that in your writing, don’t feel bad. They are one of the most common questions I get from readers, wondering when it is correct to use which word.

Which and that are both complicated words in English with many different uses inside a sentence. And while they both can be used in other constructions, the confusion between the two usually centers on their uses as relative pronouns. If you’re not sure what these are, don’t worry; everything you need is explained below.

What is the Difference Between Which and That?

Many people say the differences between these two words aren’t really differences at all. Still, many people yet swear by the traditional rule I will outline below.

That and Which as Pronouns

how-to-use-that-or-whichA brief, important note on using which or that as pronouns: be careful when using them to refer to people. Many style guides specify writers to solely use who when referring human beings and/or animals with a name. For example,

  • The woman who opened the door for you is my mom. (CORRECT)
  • The woman that opened the door for you is my mom. (WRONG)

Which and that are used, instead, for inanimate objects or animals without a name. For example,

  • The car, which had already ran out of gas, now has a flat tire.
  • The bat that I threw hit the bleachers.
  • I am sick of the dog that keeps barking.

This rule is followed by the AP Stylebook but not the Chicago Manual of Style. It’s not clear that it’s absolutely necessary, but if you are writing a paper or any piece of formal writing, it’s probably best to observe the rule.

When to Use That

The traditional American English rule regarding that and which states that that should be used with restrictive clauses and which should be used with nonrestrictive clauses.

A restrictive clause is one that is essential to the meaning of a sentence. They are also sometimes called essential clauses. A restrictive clause is used to narrow a category or identify a particular item being talked about. It restricts the meaning, making it more specific. For example,

  • All bags that are over 50 pounds will not be permitted.

The words that are over 50 pounds restrict the kind of bags you are talking about by making your sentence more specific. Without them you would be saying that no bags are permitted at all.

You should also note that restrictive clauses are not set off by commas.

When to Use Which

which-versus-that-grammarWhile that is used restrictively, which is used nonrestrictively with nonrestrictive clauses.

A nonrestrictive clause is one that is nonessential to meaning of the sentence. If you removed it, the sentence would still be understood. This doesn’t mean they are pointless; nonrestrictive clauses add some bit of extra information to the sentence. For example,

  • My bedroom, which is on the second floor, is very messy.

The words which is on the second floor add an extra piece of information about my bedroom. But if you were to remove them from the second, you would still understand that my bedroom is messy.

Nonrestrictive clauses, since they are parenthetical in nature, are always set off by commas. As you see above, there is a comma before which and after floor. These commas are very important because they can change the entire meaning of a sentence should you not have them in place.

The Chicago Manual of Style holds that which can be used restrictively when it is preceded by a preposition. For example,

  • The situation in which you put us is very dangerous.
  • The school from which I graduated is very prestigious.

Why You Need To Use That and Which Correctly

Restrictive clauses (or essential clauses) do not have commas introducing or surrounding them, but nonrestrictive (or nonessential clauses) do have commas introducing or surrounding them.

Now, as I said above, misplacing a comma when you are dealing with restrictive and nonrestrictive clauses can change the entire meaning of your sentence. The same goes for using that when you really mean which. For example, consider the following sentences,

  • My dirt bike that is green goes really fast.
  • My dirt bike, which is green, goes really fast.

The first sentence suggests that we might have more than one dirt bike and that out of our collection the green one is the fast one.

The second sentence, since the words which is green can be removed, simply informs the reader that my dirt bike is green, and it can go really fast.

It should be noted, however, that the commas in these sentences are really doing the brunt of the work, not necessarily the words which and that.

Quiz and Sentence Examples

Below are a few sentences you can use to practice,

  1. My mother was a great woman ______ always helped me with my writing.
  2. The year ______ our daughter was born was a great year.
  3. This book, ______ was written last November, is a great read.
  4. Any book ______ gets them reading is worth having.
  5. He scored 81 points in that game, ______ is hardly an easy accomplishment.

Display the answers below

Remember the Difference

A good way to remember when to use that vs. which is that “which clauses” can be removed from the sentences. You could say that you can throw out the “whiches” and no meaning will be lost.

The “thats,” however, cannot be removed from your sentences without changing the meaning.

A Note on British English Usage

I began by saying that this is a standard American English rule. In British English, writers seldom observe the distinction between that vs. which, and even though Fowler’s Usage Guide recognizes that much is to be gained by recognizing the distinction, not all British writers do.


That and which should not be used to refer to people.

That is reserved for restrictive clauses, essential to a sentence’s meaning.

Which is used with nonrestrictive clauses, nonessential to a sentence’s meaning.


  1. Who
  2. That
  3. Which
  4. That
  5. Which