Comma before “where”: Rules and Examples

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As we’ve seen in earlier posts on this topic, commas can be very confusing.

Part of the problem is that there is a lot of bad advice out there. Some people suggest adding a comma whenever you would pause while speaking.

Although this sounds like a good idea, it can lead to sentences that are ungrammatical and which may even say the opposite of what you intend.

One thing that can help is to remember that the main purpose of a comma is to clarify the meaning of a sentence.

This means that in most cases you can ask yourself if adding or removing a comma will change what a sentence says to figure out whether you are likely to need one.

In this post, we’ll walk you through how to figure out whether or not you need a comma before “where.”

 

When do you need a comma before “where”?

Where is a relative pronoun, or a word that shows some kind of relationship between the main clause of a sentence and its subordinate, relative clause.

Although “where” can show up in a bewildering variety of places, there’s a fairly simple rule you can use to check whether or not you need to put a comma first.

First, cover the clause that follows “where” with your thumb or otherwise hide it. If the sentence no longer makes sense, you should not add a comma before “where.”

If the sentence’s meaning does not change when the relative clause beginning with “where” is gone, you do need a comma.

 

“Where” and relative clauses

Because “where” is a relative pronoun, the main rule which governs comma usage is the rule for relative clauses.

Clauses are best thought of as the parts a sentence can be broken down into.

The core of each clause is a verb or action word, often accompanied by a subject or object.

The word “where” is used at the start of a specific type of clause called a relative clause.

 

When you need a comma before “where”

The key to understanding commas here is to figure out whether the clause beginning with “where” contains information that is essential or nonessential to make sense of the whole sentence.

In short, you only need to use a comma before “where” if the information that follows it is not essential to proper understanding of the whole sentence.

This typically means that the relative clause adds context or additional information that would not lead people astray if it were absent from the sentence.

 

Examples:

“I went to the library, where I borrowed a book.”

“My brother lived in Puerto Rico, where he researched cave spiders, for five years in the 1990s.”

The information in both clauses beginning with “where” in the sentences above is not essential to understanding. Because they contain nonessential information, you need to set them off from the sentence with a comma before “where.”

Note that the relative clause does not have to appear at the end of a sentence. As the second example here shows, it can also come in the middle of the main clause. In this case, you need to be sure to add a comma at the end of the clause as well.

 

When you don’t need a comma with “where”

In contrast, if the information in the relative clause that follows “where” is absolutely essential to the sentence, you should not place a comma in front of it.

 

Examples:

“I went to the library where I borrowed a book.”

“The astronaut landed on the moon of Saturn where she had parked her spaceship.”

 

In these examples, the information that follows “where” is essential to understanding the sentence.

Saturn, for instance, has at least 82 moons. This means we need to know which moon the astronaut landed on.

Likewise, there may be any number of libraries the speaker of the first sentence could visit, and the lack of comma clues readers into which specific library.

In short, the lack of a comma before “where” tells readers that what comes next will provide details they cannot skip.

 

“Where” and restrictive clauses

You might notice that the example about libraries is used in both sections above with the only difference being the inclusion of a comma.

If you’re trying to figure out if you need a comma based only on the word you use, that can seem like a nightmare.

In fact, this problem makes it clear that you need to understand the grammar behind the word you’re using, rather than memorize arbitrary rule.

In our library sentence, the real difference is in the meaning of the relative clause “where I borrowed a book.”

Clauses can sometimes be what is known as a “restrictive clause,” meaning it serves to tell the difference between one thing and all the other things like it.

If a clause is not restrictive, on the other hand, it is most often providing contextual information about something else in the sentence.

As we have seen with our library sentence, adding a comma changes the meaning of the sentence considerably.

Let’s look a little more closely at the difference in meaning, and how the comma changes things.

 

Example:

“I went to the library where I borrowed a book.”

 

This sentence is an example of a restrictive clause. In other words, “where I borrowed the book” identifies which specific library the speaker visited.

There might be any number of other libraries that could be confused with the specific library to which the speaker is referring.

Because removing the relative clause would change the meaning of the main clause (you can’t tell which library without that information), you shouldn’t add a comma.

 

“I went to the library, where I borrowed a book.”

 

This sentence is not a restrictive clause. “where I borrowed a book” does not identify a specific library, but describes what the speaker did upon arriving at the library.

Although we still might not know which library the speaker went to, it doesn’t change the main point of the sentence, which is just that the speaker did go to the library.

In other words, because removing the relative clause would not change the meaning of the main clause you do need to add a comma before “where” in this sentence.

If you still find yourself getting confused about commas and the word “where,” just remember the following basic rule: Don’t add a comma before “where” unless what follows it is not essential information.