What Do They Have in Common?
If we want to combine two clauses (a group of words that includes a subject and a verb, and forms a sentence or part of a sentence) together, we can use a relative pronoun. In the English language, we have three main relative pronouns:
|that||Humans and Non-humans|
'That' for People or Things
The relative pronoun 'that' is very flexible and you can use it for people or things.
'Which' Only for Things
The relative pronoun 'which' can only be used with non-human objects.
That or Which?
'Which' and 'that' can both refer to non-human things, but the meaning of the sentence can change depending on which one you use.
How Do We Choose?
If you want to know how to decide between choosing 'which' or 'that', first you need to know about the 'essential' and 'non-essential' clauses.
An essential clause (also called restrictive clause or defining clause) means that the information in the clause is essential or necessary for us to understand the preceding noun.
A non-essential clause (also called nonrestrictive clauses or non-defining clauses) is not essential to the meaning of the whole sentence. You can easily omit it and your sentence would still be meaningful.
How to Choose between That and Which
To choose between 'that' and 'which', remember this golden rule:
For an essential clause, use 'that.'
For a non-essential clause, use 'which.'
When to Use 'That'?
We use 'That' in essential clauses. Here's some examples:
Here, we understand that Alina has several necklaces, so it's essential to distinguish the one that looks like a heart from others.
In this sentence, since not all boots are used for mountain climbing, we use that to indicate the essential information.
Pay attention that the essential clause doesn't always come immediately after the noun.
The book in the top shelf
Here, it means that there are multiple books in shelves, thus it's essential to mention which book.
When to Use 'Which'?
We use 'Which' in nonessential clauses (the information in the clause isn't necessary to understanding the noun in the sentence). Here are some examples:
In this sentence, the information about Mathew's bedroom being light blue is not essential to the sentence. Mathew only has one bedroom, so the extra information doesn't contribute to identifying it. Therefore, we use 'which.'
The Use of Commas
Another important difference between essential and non-essential clauses is the use of commas. We use commas in non-essential clauses to separate it from the rest of the sentence.
Sally's favorite restaurant,
Again, the information about the view of the restaurant is not essential for understanding the rest of the sentence. We can omit the non-essential clause and still understand the sentence perfectly.
What Happens When We Replace 'That' with 'Which'?
Now let's look at some of the earlier examples and see how the meaning can change if we replace 'that' with 'which' and vice versa.
First, let's replace 'that' with 'which':
In this sentence, changing to which causes the sentence to imply that Alina only has one necklace.
Here, the sentence has changed to imply that the primary purpose of all boots is climbing. Because not all boots are used for mountain climbing, the sentence is not true.
What Happens When We Replace 'Which' with 'That'?
Now, let's switch 'which' with 'that' and see how the meaning of the sentence can change:
Here, it implies that Mathew has several bedrooms, therefore it is essential to specify the light blue one.
Sally's favorite restaurant,
Sally's favorite restaurant
In this example, changing which to that shows that Sally is interested in many restaurants that have great views, and the sentences specify that her favorite is in King of Prussia Mall.