[Sticky] The Essential Guide to Proper Use of 'That' and 'Which' in English Grammar

"That" and "which" are two of the most commonly used relative pronouns in the English language. While they may seem interchangeable, they actually have distinct functions and should be used in different situations.

The main difference between "that" and "which" is that "that" is used to introduce essential or restrictive clauses, while "which" is used to introduce non-essential or non-restrictive clauses.

Essential clauses are also known as restrictive clauses, which means they provide necessary information to identify the subject being referred to. These clauses cannot be removed from the sentence without changing the meaning of the sentence. In this case, "that" should be used to introduce the clause.

For example: "The book that I am reading is very interesting." In this sentence, the clause "that I am reading" is essential to identify which book is being referred to. Removing the clause would result in an incomplete sentence: "The book is very interesting."

Non-essential clauses, on the other hand, are also known as non-restrictive clauses. These clauses provide additional, but not necessary, information to the sentence. In this case, "which" should be used to introduce the clause.

For example: "My favorite book, which was written by J.K. Rowling, is Harry Potter." In this sentence, the clause "which was written by J.K. Rowling" is not essential to identify the subject being referred to, but it provides additional information. Removing the clause would still result in a complete sentence: "My favorite book is Harry Potter."

It is important to note that non-essential clauses are set apart from the rest of the sentence with commas. Essential clauses, on the other hand, are not set apart with commas.

Here are some more examples to illustrate the difference between "that" and "which":

• "The car that I bought last week is a hybrid." (Essential clause)
• "The car, which is parked in the garage, needs to be washed." (Non-essential clause)
• "The company that I work for is based in New York." (Essential clause)
• "The company, which was founded in 1990, has over 500 employees." (Non-essential clause)

In summary, "that" is used to introduce essential or restrictive clauses, while "which" is used to introduce non-essential or non-restrictive clauses. Paying attention to the distinction between these two pronouns can help you write clearer and more concise sentences.