The Difference Between Which & That
Grammar – the mere sight of the word frightens many people. It's very understandable, given the large number of exceptions and rules that exist in the English language. One of the issues that has perplexed native and non-native English speakers for many years is correct usage of the words "which" and "that." It is often difficult for people to know when to use these two similar terms.
The term "which" is used in sentences containing non-restrictive or relative clauses. This refers to cases where additional information is supplied about a person or object in the sentence. You can remove the clause without changing the meaning of the main clause.
"I would like to buy the cake, which contains the yellow frosting."
For this particular sentence, you are referring to only one cake. In this case, it's the one with the yellow frosting.
"The play, which was performed in the Broadway theatre, was a huge success."
In this sentence, the writer assumes that the reader is already familiar with the play that is being discussed. You can remove the term "which" and still retain the same meaning.
You should use the term "that" with sentences that contain restrictive clauses. If you remove the clause from these particular clauses, the meaning of the sentence will be changed.
"I would like to buy the cake that contains the yellow frosting."
This means that you want the specific cake with the yellow frosting, rather than any cake. If you remove the restrictive clause that from the sentence, it will change the meaning entirely.
"The play that was performed in the Broadway theatre was a huge success."
This sentence is describing the play because the writer assumes that the reader will not know which one it is. You can't remove the word "that" without changing the meaning of the sentence so you know you're using the correct term.