Adescribing how to correct common grammar and writing mistakes. Their explanation of the difference between has some dry humor:
"He said that that ‘that’ that that man used was wrong."
If you understand this sentence, you probably don’t need to read on. If you don’t, you could be one of the many who are a bit hazy on how and when to use the word ‘that’. It’s a versatile little beast, with many uses. The one that people most often get wrong is the use of ‘that’ as opposed to ‘which’.
Here at Right Words, we engage in ‘which’ hunts, because what usually happens is that people use ‘which’ when they should use ‘that’.
The difference is this. ‘Which’ introduces relative clauses – ones that give additional information about something in the sentence, and that can be added or removed without affecting the statement made in the main clause.