Do you get frustrated trying to work out whether to use which or that?
A lot of people find it confusing, so you’re not alone.
Let’s look at it here with examples.
Which and that can both function as relative pronouns – don’t lose interest because I used a grammatical term.
Bear with me and I’ll show you the difference between these two words.
But first, let’s break it down and look at what a clause is and what a sentence is.
There are four types of clauses – but there are two things they all have in common.
They all contain a subject and a verb.
A subject is the person or thing being described or doing the action.
A verb is a ‘doing word’ that expresses the physical action, a state of being or a mental action.
A sentence is a group of words that has a complete meaning within itself.
It typically contains a subject and a predicate
(the part of the sentence that contains the verb saying something about the subject),
and it conveys a statement, command, exclamation or exclamation.
A sentence contains a main clause and one or more subordinate clauses.
When it comes to making a decision about which or that, there are two scenarios to consider.
You need to work out whether the relative pronoun – which or that – is introducing a non-essential relative clause or an essential clause.
An essential relative clause is one that is essential to the meaning of the sentence.
If we take the essential relative clause out the sentence it will be affected.
In fact, the sentence won’t make sense or be complete without it.
For example – The passenger boarded the bus that was filled with tourists and suitcases.
In the sentence above ‘that’ is introducing the essential relative clause.
It contains essential information about the noun that precedes it.
So if we remove ‘that was filled with tourists and suitcases’, the sentence won’t be complete or make sense.
This is how we know to use ‘that’ and not ‘which’ – the information after ‘that’ is essential to the meaning of the sentence.
‘That’ is an important indicator of an essential clause because it introduces important details to the sentence.
The computer that Jack left at the sports shop turned up at his house today.
Now let’s look at non-essential relative clauses and the role of ‘which’.
Non-essential relative clauses contain added information that can be left out without affecting the meaning of the sentence because it’s considered decorative and non-defining.
For example – I noticed the garden was full of pastel-coloured roses, which were perfumed and lovely.
If we leave out ‘which were perfumed and lovely’, the sentence still makes sense. It might not contain as much information, but it still functions as a sentence.
Sometimes the non-essential clause is in the middle of a sentence, not at the end of it.
For example – I went to see A Star is Born, which starred Lady Gaga, and I thought it was great.
In this sentence ‘which starred Lady Gaga’ is the non-essential relative clause.
It can easily be left out of the sentence without affecting the completeness or the meaning.
Sure it leaves out some interesting information – but it still functions as a sentence.
This is how we know it is a non-essential relative clause and we should use ‘which’ not ‘that’.
There is one vital detail that must be considered when using ‘which’ for non-essential clauses in sentences.
A comma should always precede ‘which’ unless it is preceded by a preposition (in, to, on, after, for, with, under etc).
For example – The church, which was being rebuilt, was not open for visitors.
Note: it is also okay to use spaced en dashes instead of commas.
For example – The church – which was being rebuilt – was not open for visitors.
A sentence with a non-essential clause with have either two commas framing it or one comma and a full stop.
Today I walked to the market, which was five blocks from my apartment.
Today I walked to the market, which was five blocks from my apartment, to buy some mangos.
If you are trying to work out whether to use which or that, try inserting a comma before ‘which’ and if it doesn’t make sense you know to use ‘that’ instead.
The Prime Minister was in a meeting, which required the attendance of the Minister for Health. (Incorrect)
The Prime Minister was in a meeting that required the attendance of the Minister for Health. (Correct)
Inserting a comma above before ‘which’ shows us that we’re using the wrong word, but if you substitute which for that the sentence doesn’t require the comma and is more meaningful.
Remember, if you insert a comma before ‘which’ does the sentence still make sense?
If it doesn’t, it means you should replace ‘which’ with ‘that’.
For example – The shop that sells fresh flowers is always preferable to one which sells chocolates. (Incorrect)
For example – The shop that sells fresh flowers is always preferable to one that sells chocolates. (Correct)
The Australian Government Style Manual provides the following examples to demonstrate how using which or that incorrectly can change the intended meaning of a sentence.
The research findings that were likely to cause embarrassment were never circulated.
The sentence above makes it clear that the research findings not circulated were the ones likely to cause embarrassment.
The research findings which were likely to cause embarrassment were never circulated.
The sentence above is ambiguous – were all the findings withheld or just the embarrassing ones?
The research findings, which were likely to cause embarrassment, were never circulated.
It’s obvious that none of the recommendations were circulated.
In the first example, the use of ‘that’ makes it a defining or essential relative clause – so it provides defining, essential information that defines the subject.
The second example is ambiguous and you shouldn’t write sentences like this.
The third example, with the pair of commas framing the clause, is a non-essential relative clause.
The information inside the commas is decorative and not essential to the main point.
Deciding whether to use which or that should be clearer now.
It’s like the two cups of coffee in this photo. They appear to be the same, but there are subtle differences that could get you into trouble.
If you drink your coffee out of the cup on the right, you might be bargaining for more than you can manage.
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