Which or That? The grammar rules

In certain phrases in English, you can use “which” or “that” such as, “Monday is the day that/which I hate the most!” However, sometimes you can only use “which”. For example: “I’m from Moscow, which is the capital of Russia.”

The good news is that you can always use “which”, although most native English speakers prefer to use “that” whenever it’s possible. In this blog, we’re going to examine the grammar rules that govern the use of these annoying little words that cause so much confusion for students.

From First Certificate in English level onwards, you will be expected to be able to understand and use these words correctly and may be graded on your use of them in both the Writing and Use of English papers.

To clarify, we are not talking about the use of “which” as a question word (e.g. Which is bigger; Italy or France?) but as a linking word in subordinate clauses.

Subordinate clauses

A subordinate clause is a clause which functions as part of another clause (e.g. as subject, object or adverbial in the main clause of a sentence). Simplified, a subordinate clause is part of a bigger sentence and exists to define the subject or object, or to provide extra information. Look at the following examples:

1. Subordinate clause defining subject:
   

   “The city that/which I love the most is Barcelona.”

   In this example, the subordinate clause is underlined and it forms part of the subject. You can use “that” or “which” in this sentence. Imagine the sentence without the clause: “The city is Barcelona”. This sentence is grammatically correct but lacks meaning. It is ambiguous. Therefore, the subject of the sentence should be “The city that I love the most…”. In this case, the subject is defined and the sentence has meaning.

2. Subordinate clause defining object:

   “I love languages that/which are easy to learn.”

   In this example, the subordinate clause underlined forms part of the object. Without the clause, the sentence is just “I love languages” which isn’t quite what the speaker is trying to say. Again, in this example both “that” and “which” are possible.

3. Subordinate clause providing extra, non-essential information:

   “My car, which is 10 years old, needs to be repaired regularly.”

   In this example, the subordinate clause is providing extra information, which is neither defining the subject or the object, nor is the information essential to the meaning of the sentence. Imagine the sentence without the subordinate clause: “My car needs to be repaired regularly.” The meaning of the sentence here is the same. The subject is clearly defined. True, the sentence has a little less information but it doesn’t affect the meaning. In this example, only “which” is possible.

Also, notice the comma separating the subordinate clause from the subject. Although the subordinate clause here relates to the subject, it is not part of it. Therefore we use a comma to show this separation.

These three examples are essentially the three types of subordinate clause. Numbers 1 and 2 are examples of what are known as “defining clauses” while number 3 is an example of a “non-defining clause”.

Conclusion

1. Remember, clauses that define the subject or the object can be introduced with “which” or “that”. It is useful to know that most native English speakers prefer to use “that” in these cases.
2. Clauses that simply provide extra information can only be introduced with “which”. It is useful to recognise that such clauses are more common in written English than in spoken English.
3. When using a non defining relative clause with “which”, you need to use a comma to separate the clause from the subject or object.

N.B. “Which” and “that” are not the only words that introduce subordinate clauses. There are also “who”, “where”, “when”, “whose”. However, “which” and “that” are the most common relative pronouns used to define or give extra information about things, while the others are used for people, places, time and possession respectively.

If you’re a visual learner, have a look at this well made video on the subject from Jane Penson’s business writing blog.

Don’t forget to post your comments or questions below if you found this blog useful or want to ask about anything relating to the subject. Also, let us know if you would like us to explain any other grammar points as we are always looking for subjects to blog about that are most useful to our readers.

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