What is the difference between that and which?
While both words are used to add information to a noun, they are not interchangeable. This article informs you when to use which word.
You may have learned that 'that' is for essential information, while 'which' is for additional information.
Proper nouns
In most cases, only additional information can be added to proper nouns.
For example:
For example:
- He is from China, which is the most populous country in the world.
- 'is the most populous country in the world' is not essential information to 'China', because China is still China even if India becomes the most populous country.
Common nouns
If the noun is a common noun, the two methods below will help you figure out whether to use 'that' or 'which'.
Method 1: If the clause is removed, does the sentence retain its meaning?
Method 2: Consider whether there is more than one of the noun.
Method 1: If the clause is removed, does the sentence retain its meaning?
- The conference, which was held in Melbourne over two days, attracted people from around the world.
- The conference attracted people from around the world has the same meaning (with less information).
- Reading books that use many long words is difficult for him.
- Reading books is difficult for him has a different meaning.
Method 2: Consider whether there is more than one of the noun.
- My phone that/which is more than five years old died today.
- If you have one phone, use which because 'my phone' is sufficient information to know what phone you are talking about.
- If you have two phones, use that because 'my phone that is more than five years' differentiates it from your other phone.
Please note that, when a that-phrase ends with a preposition, 'that' can be substituted with the preposition + 'which'. For example, The university that she studied at is in this city = The university at which she studied is in this city.
