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Which vs. That — The Definitive Guide

Which vs. That — The Definitive Guide

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One of a writer’s greatest weapons is his or her solid footing on grammatical concepts, including sentence structure, lexis, and stylistics.

A writer connects his or her internal thoughts to the reader through textual characters that represent a whole unit of meaning.

This whole unit of meaning can also be dissected in parts in order for people to comprehend how it is formed.

In today’s text, we’ll focus on these intricacies, particularly in using “which” and “that,” which often causes confusion among native and non-native English language users.


What’s the difference between using “which” and “that”?

When using “which” vs. “that” as relative pronouns, the difference is in the essentiality of the information introduced. A piece of essential information leans more toward using “that,” especially in American English. But, a non-defining or non-restrictive clause is conventionally headed by “which.”


Grammatical essentials on “which” and “that”

To understand the holistic meaning of sentences containing “which” and “that,” it is essential that we also know their individual differences and senses.

Apart from the spelling and pronunciation, the exact senses of “which” and “that” can be differentiated by how they are used within a sentence.

Let’s look at each of them in detail.



“Which” can be identified as an interrogative pronoun, a relative pronoun, or a determiner in a sentence.

As an interrogative pronoun, “which” is used to replace a noun in asking a question, such as in the following sentence:



So, which would you prefer then?


Or, “which” also be used as a determiner that identifies or refers to a noun in a sentence.




I can’t decide which watch I should buy.


And, “which” may also be used as a relative pronoun to refer back to an antecedent, a noun that precedes a relative clause.




Garden of Beasts, which is one of Jeffery Deaver’s most successful works, is a consummate thriller.



“That” is a flexible word that can be used in at least five different senses or meanings, functioning as a subordinating conjunction, relative pronoun, demonstrative pronoun, determiner, or adverb.

As a conjunctive device, “that” is used to form a complex sentence structure that is made up of at least one independent and one dependent clause.




We didn’t know that he was sick.


“That” can also be used as a relative pronoun, a pronoun that introduces an adjective clause that refers back to a mentioned noun; this noun is also called an antecedent.




This is a song that my teacher wrote before she passed away due to cancer.


As a demonstrative pronoun, “that” is used to refer to any singular entity that is far or distant from the reference point of the speaker or writer.




What is that?


The determiner “that” works as an adjective when it predetermines a noun, and thus, it can be found before a noun when used in a sentence.




That plant is poisonous.


Lastly, “that” may also behave as an adverb, particularly called an intensifier, when it is informally used to mean “very” or “really” but with a context-dependent intensity.




What you said isn’t that funny.


“Which” vs. “That” in clauses

Now that we’ve seen how “that” and “which” work in sentences, it is pivotal that we also focus on the part that baffles most people, that is, the use of “which” versus “that” in introducing relative clauses.

The easy way around this catch-22 situation is to gauge and determine how essential the clause is, with respect to the writer’s intended implication and effect.

This suggests that depending on the sentence’s structure and style, as well as the context, the clause introduced by “which” or “that” can either be essential or non-essential to the sentence’s holistic unit of meaning.


“That” and defining or restrictive clauses

At least in American English, the grammatical convention is to use the relative pronoun “that” in introducing a defining clause.

A defining clause is also known as a restrictive clause, and it bears some information that is “essential” to the entire sentence.

Since the clause is essential, then it means removing it would cause damage to the whole unit of meaning conveyed by the writer.

Here’s an example to demonstrate the explanation.




The man that lives in 405-B just passed away this morning.


In the sentence above, the clause “that lives in 405-B” is essential to specify the antecedent which is “the man.”

And, this is so because we don’t want to just point out any man in the building; instead, we want to refer to that exact person who used to live in 405-B.

Thus, removing the clause would cause some ambiguity to the reader, especially without any other pieces of information provided.


The man just passed away this morning.


Yes, the remaining parts still make up a perfectly grammatical sentence because it contains a complete subject and predicate.

But, with this information alone, can we identify the man being meant by the writer? Do we have sufficient information to know who this man exactly is?

If you answered “no,” then you may stop reading here, as you’ve already understood half of the discussion. The rest is just self-explanatory.

Kidding and digression aside, let’s also compare the that-clause above to the non-defining clause elaborated below.


“Which” and non-defining or non-restrictive clauses 

As you may have guessed, a non-defining clause is not as grammatically essential as the defining one, and therefore, this is otherwise known as a non-restrictive clause.

Put simply, it only bears an additional piece of information that refers back to the antecedent, which is, again, a preceding noun.

Ostensibly enough, a non-defining clause meanwhile bears non-essential information, thereby not causing any ambiguities when removed.

In cases like this, the clause should be encapsulated with two commas when it appears mid-sentence.

Of course, only one comma should set it off when it appears towards the end of the sentence.

Here’s how that goes.




Jeffery Deaver’s Garden of Beasts won a CWA Ian Fleming Steel Dagger award for the best thriller of 2004, which is remarkable.


If we analyze the sentence above, the clause “which is remarkable” only serves as supplemental information to the previous clause.


Let’s also try removing to see the difference.


Jeffery Deaver’s Garden of Beasts won a CWA Ian Fleming Steel Dagger award for the best thriller of 2004.


Now, would you still understand the juice of the message without the which-clause?

If you’re nodding your head while reading, then you’ve already got this.

However, as languages are inherently arbitrary, we do not necessarily have or stick to only one rule.


The essential “which”

If you’re also wondering why “which” may not be preceded with a comma at times, this subsection is the answer to your query.

Do you sometimes notice that “which” is used as prepositional objects as in phrases like “in which,” “of which,” or “by which”?

This is the clearest comma distinction rule we can draw out from this enigma, thereby suggesting not to place a comma before “which” when it is preceded by a preposition.

Regardless of whether the clause being introduced is essential or not, “which” should never be preceded by a comma at all.

However, a comma may or may not precede the preposition, e.g., in, on, at, by, from, instead.




The hospital in which I was born has been demolished.


Other considerations to take on essentializing “which”

Furthermore, it is also crucial to note that British English somehow operates differently from American English, therefore, the grammatical conventions aren’t the same all the time.

Some British writers and other followers of BrE may arbitrarily use “which” in introducing essential clauses, and hence the confusion.

Also, other writers may want to create certain effects on their readers through written language, such as emphasis, humor, or register shift.

These reasons also explain why “which” is deliberately used to introduce a relative clause without a pre-comma.

After all, comma decisions are not necessarily set in stone, and writers are expected to be creative. Therefore, sentences can be adjusted according to the purpose of the text.

So, if you’re here checking for some clear, standardized rules for the sake of academic and business writing, then I suggest sticking with the American English rules.

That’s also the main reason why most writing style guides are American-based, simply because of an existing set of clear and often rather rigid yet organized yardsticks.

But, if you’re here for literary writing purposes, I would say that you should never limit your creativity to certain grammatical conventions, so long as you’re also not deliberately breaking them for misinformation purposes.

Frequently Asked Questions on “Which” vs. “That”


Should we use “which” or “that” in plural subjects?

The antecedent’s number does not determine the choice between using “that” and ”which.” However, the verb should agree with the preceding noun’s number instead.


What is the rule differentiating the use of “which” vs. “that”?

In a nutshell, defining or restrictive clauses make use of “that,” whereas non-defining or non-restrictive clauses use “which. A defining clause is essential to the sentence’s whole unit of meaning, while the other type isn’t.


When can we use “that” instead of who?

In informal English, the relative pronoun “that” is often used as a catch-all substitute for other relative pronouns including “who.”



The confusion between using “that” and “which” suggests that the English language is alive and thriving with civilization.

Thus, at the end of the day, it is always beneficial to keep enhancing our stock or preexisting knowledge updated.