The Difference between “that” and “which”
“That” and “which” are not interchangeable. Although their individual meanings seem similar they are used quite differently. To understand the difference between the two, you should first understand relative clauses.
In simple terms, a relative clause acts like an adjective by providing additional information about someone or something. Sometimes a clause merely provides additional information but is not necessary to the purpose of the sentence (non-restrictive clause), however, at other times the relative clause is necessary to understand the meaning of the sentence (restrictive clause).
“That” is used when the clause is restrictive, and “which” is used when the clause is non-restrictive.
I know this still sounds a little confusing. Look at restrictive and non-restrictive clauses in action and also notice that the punctuation is different in the two cases.
- Apples, which are red, are my favourite fruit.
- Apples that are red are my favourite fruit.
Read the above two sentences a few times. Do they mean the same thing?
They look very much alike but they are different in meaning.
The first sentence, (Apples, which are red, are my favourite fruit.) This sentence means that apples are my favourite fruit, and a description of apples is also given. Apples are red. We would call this a non-restrictive clause because there are no restrictions.
The second sentence (Apples that are red are my favourite fruit.) This sentence has a very different meaning because there is now a restriction. Only red apples (not green or yellow or any other colour), are my favourite fruit.
If the clause isn’t vital to the meaning of the sentence, and is only there to provide additional description use “which”.
If the clause is vital to the meaning of the sentence use “that”.
I hope this clears up any confusion as to the difference between “that” and “which”.