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Comma before “which” — A Comprehensive Guide

Comma before “which” — A Comprehensive Guide

For many, commas are a hard nut to crack, but they don’t have to get into our nerves at all.

Tech people may compare computers to human beings, while, in language, commas are also just like shelves that keep books from being a cluttered mess.

Today, we’re going to discuss one of the most commonly used words in English, as well as how to punctuate it with a pre-comma appropriately, which is “which.”


When is a comma necessary before “which?”

A comma before “which” is necessary when it introduces nonrestrictive information either midsentence or towards the end of it. Nonrestrictive information refers to any additional, emphatic remarks that are grammatically dispensable or removable from the rest of the sentence. Also, when a nonrestrictive idea comes midway, the closing comma should automatically precede “which” when it subsequently follows to introduce further details in the sentence.


Guidelines on placing a comma before “which”

The shorthand process that leads to a successful pre-comma decision to “which” is to determine the essentiality of the information it introduces.

Especially in American English, the comma “rule” regarding this word is pretty easy to digest because of an existing grammatical convention.

The default analysis in AmE suggests going back to the idea of placing a comma before “which” when it introduces a nonrestrictive or nonessential remark.

Whereas, the other rule suggests using “that” instead of “which” for restrictive information.

Nonrestrictive remarks are emphatic and syntactically removable, in which commas serve as the tool that the writer uses to represent such features.

Knowing when to place a comma before “which,” therefore, can be achieved by identifying nonrestrictive or nonessential information.

Let’s look at nonrestrictive information in detail below.


When “which” introduces sentence-medial, nonrestrictive information

When we describe ideas or information as nonrestrictive, it means that they have been used by the writer for the sole purpose of adding clarity or emphasis to the statement.

As they are additional elements, they can make the text more interesting to read, not to mention non-monotonous.

In other words, nonrestrictive remarks work like written accessories that beautify what the writer intends to convey.

In real life, pieces of jewelry are generally worn to increase the sense of self-confidence because it makes the wearer feel more attractive.

But, not wearing these accessories does not necessarily mean that the wearer won’t survive for a day, a week, or even a month.

The written language does have its own ways to express such features. So, please refer to the next example to see how “which” may introduce a grammatically inessential remark.

Mom’s new phone, which was only bought last week, fell in the tub.

A pre-comma is necessary before “which” in the example above because it introduces a nonrestrictive adjective clause that describes the subject in the sentence.

Let’s try taking the clause away.

Mom’s new phone fell on the tub.

Put simply, the information left still makes complete sense, and it has retained the details necessary to convey the intended meaning.


When “which” introduces sentence-final, nonrestrictive information

The nonrestrictive clause may also come at the end of the sentence, and likewise, a pre-comma should be placed before “which” in this structure.

The keys are in the blue purse inside my bag, which is on the countertop.

The which-clause provides further information about the object “bag” that helps the reader understand the information better.

As the sentence would still make full grammatical sense without the last clause, then it is considered nonrestrictive.

In the context of the last example, we can also deduce that nonrestrictive information, albeit grammatically inessential, does help a lot in making statements clearer to understand.

Hence, although which-remarks can be just additional details sometimes, they still facilitate a lot in disambiguating meaning. 


When “which” appears after non-restrictive information

Now, we already know that we can add extra information halfway through the sentence by encapsulating it with commas, right?

This also means that a which-clause appearing after a mid-sentence nonrestrictive remark should be automatically preceded with a comma.

The pre-comma to “which” is simply the same comma that is used to end the nonrestrictive information positioned midsentence.

Here’s an example.

He has become obnoxious after the divorce, especially upon knowing who Emma is dating, which was also his fault in the first place.

Technically, the which-clause at the end of the sentence is also just another nonrestrictive clause added for the sake of commenting on the incident described.

The initial clause already bears complete meaning per se.

He has become obnoxious after the divorce.

But, as humans are intelligent and creative, while language is recursive at the same time, then it is possible to continuously construct ideas based on how we understand events.

In a nutshell, we can say that our ability to add extra details in sentences highlights the collaborative power between human thought and language.


The incorrect comma placement before “which”

Now, let’s also have a look at the conditions that make the comma placement inappropriate so that we can ooze out every nook and cranny of the topic being discussed.

Enumerated below are the four conditions that guide the non-placement of the comma before “which” in sentence construction.


When “which” introduces restrictive information

“Which,” may also introduce restrictive information or an idea that is highly essential to the grammaticality and meaning of the whole sentence.

When this happens, it means that the writer treats the information as utterly indispensable to the holistic meaning of the sentence.

Please study the next sentence.

The novel which is on the topmost shelf has the best plot ever written.

In the example above, the which-clause is essential to the holistic meaning of the entire sentence because it bears meaning that can ambiguate the sentence when taken out.

The novel has the best plot ever written.

Considering what’s left in the sentence above, any reader given this information alone will be confused about the exact item being referred to.

Therefore, the which-clause is necessary to do such a task, and no comma should appear before “which.”


When “which” comes after a preposition

Another condition that guides the non-placement of a pre-comma is when a preposition comes before “which.”

Especially in formal writing, dangling prepositions are generally frowned at because they are more likely used in casual discourse.

The prepositions that often appear before “which” are “in,” “of,” and “with,” forming “in which,” “of which,” and “with which,” respectively.

In this case, the essentiality or nonessentiality of the information being introduced by these formal prepositional phrases becomes irrelevant when it comes to the comma decision.

Automatically, the pre-comma placement rule should apply before the preposition rather than “which” this time.

Here’s an example of restrictive information introduced by “in which.”

We went to a museum in which genocide victims’ remains are kept.

And, here’s a nonrestrictive one.

The remains of the genocide victims are kept in a museum in Vilnius, in which messages of despair can be seen on the cell walls.

Again, a comma must not be placed before “which” in other similar sentences regardless of whether the clause is essential or not.

However, the comma may be placed before the preceding preposition instead.


When “which” is used in an indirect question

Thirdly, a comma should also not be placed before “which” when it is used in an indirect question.

An indirect question is a type of reported speech that we use to pass on a question or inquiry from another person by turning it into a sentence in its declarative form.

Here’s an example question.

Peter: Cath, can you ask Mike which country Rosie is in?

And, here’s how we can turn it into an indirect question.

Cath: Hey, Mike. Peter’s asking which country Rosie is in.

The examples above are also making use of dangling prepositions, which should be fine because of the informality of the context of discourse.

In indirect questions, we can simply assume that any information introduced by “which” is essential for us to transfer the complete meaning of the original question.

And thus, no comma should appear before it.


When using the phrase “which is which”

Lastly, we may also use the relatively common phrase “which is which” to emphasize the indistinguishability of items.

In the example below, a comma is not placed before either the first or second “which” because the phrase is the direct object of the second clause, which is a part of the complete predicate.

To me, all plants look the same, but my mom can easily tell which is which.

Of course, our grammatical acuity would tell us that this condition remains valid unless “which is which” is used as a nonrestrictive remark or when it starts the sentence off.

In informal conversations, “which is which” may also refer to a person rather than an item or animal only.

I’m sorry, but all these babies look the same to me, so I can’t really tell which is which.

But, apparently, no mother would probably be hearing your usage of “which” instead of “who” in the context of the example above.

So, we had better use “which” and “who” appropriately.


Which vs. That: In relative clauses

As mentioned sections ago, the convention in American English suggests sticking with “which” for nonrestrictive information and “that” for anything indispensable.

However, this shorthand rule may create readability issues when recklessly applied.

The better option is to analyze the information according to its grammatical relationship with the other sentence elements.

When we start looking from this angle, won’t be worrying about “which” vs. “that” only but also other words like “who,” “where,” “when,” etc.

But, for the sake of explaining the difference between “which” and “that,” we can bear in mind that “which” can introduce either restrictive or nonrestrictive adjective clause.

But, the relative pronoun “that” is only used in introducing a restrictive adjective clause and not in a nonrestrictive one.

Again, we can always try removing the information from the sentence to see whether what remains will still make sense.


Frequently Asked Questions on “Which”


When do we need a comma before “which includes?”

We need a pre-comma before “which includes” when it introduces grammatically dispensable information in the sentence as in, “Your premium gym subscription allows you to use all the equipment and services in the facility, which includes our newest program on yoga handstands.”


What is the difference between “which” and “what?”

The main difference between the “which” and “what” is the number of choices available, wherein limited options entail the usage of “which,” and an unlimited or wide array of choices need to use “what.” For example, we say “What is your name?” but “Which is better, A or B?”


How can we use “in which?”

We use “in which” to formalize sentences in passive voice that contain dangling prepositions. For instance, the phrase “the city which she lives in” can be turned into “the city in which she lives.”



If you’ve reached this part of the post, I bet you’ll never have to worry about whether you need a comma before “which” anymore.

Yes, comma decisions can sometimes be nerve-racking, but if you keep spending your time reading articles covering such topics, then you’ll certainly be able to understand the patterns in no time.