“Which” vs. “Comma + Which”: Modifying a Noun or a Clause

“Which” and “Comma + Which”

When you read English texts, you may notice two common uses of “which”:

• simple “which”
• comma + “which”

In some contexts, the difference in meaning between them may seem slight. However, if you want to understand complex English texts accurately, it’s important to recognize how these two patterns differ.

In this article, we will explore how the relative pronoun “which” changes its meaning and function depending on whether it’s used with a comma. We will also look at how to use these patterns effectively in writing and speech.

Relative Pronoun “Which”

In English grammar, “which” is often used as a relative pronoun to give additional information about a preceding noun or idea. This use is different from the question word “which,” as in “Which bag is heavier?”

When “which” is used as a relative pronoun, it connects a relative clause to an earlier word or idea in the sentence.

There are several common relative pronouns in English:

As you can see in the table, the relative pronoun “which” is usually used when the preceding element refers to something other than a person. If the preceding word refers to a person, “who” or “whom” is usually more appropriate, depending on the grammatical role in the relative clause.

What Comes after a Relative Pronoun

A relative pronoun introduces a relative clause. A relative clause is a dependent clause, not an independent clause. This is because a relative clause can’t stand alone as a complete sentence. It depends on another noun or idea in the main clause to complete its meaning.

For instance, you can’t say only “which makes me happy” as a complete sentence. The listener would naturally ask, “What makes you happy?” The clause needs an earlier noun or idea to refer to, as in the sentence “This is a movie which makes me happy.”

Now, let’s look at the ungrammatical sentence below:

× I have a cat which cute.

The relative clause in this sentence can be analyzed as follows:

• Subject: the relative pronoun “which,” referring to “a cat”
• Verb: missing
• Complement: “cute”

Since the relative clause lacks a verb, it’s ungrammatical. The word “cute” is an adjective, so it can’t function as the verb of the relative clause. To make the sentence grammatical, we need to add a verb:

I have a cat which is cute.

Now, the relative clause has the following structure:

• Subject: the relative pronoun “which,” referring to “a cat”
• Verb: “is”
• Complement: “cute”

Inside the relative clause, “which is cute” forms an SVC structure. The relative clause is still dependent because it refers back to “a cat,” but its internal grammatical structure is complete. That is why the revised sentence is grammatical.

Clear Definition of “Which” and “Comma + Which”

Let’s go over the difference between “which” without a comma and “comma + which.”

• “Which” without a comma: This type of “which” usually modifies the noun or noun phrase immediately before it.
• “Comma + which”: This pattern adds extra information. In many cases, especially when the “which” clause describes a result or consequence, “which” can refer to the whole idea expressed in the previous clause.

The comma changes the role of the relative clause. Without a comma, “which” usually helps specify the noun before it. With a comma, the “which” clause adds supplementary information and mainly refer to the whole preceding idea.

“Which” Without a Comma

When the relative pronoun “which” is used without a comma, it refers to the noun or noun phrase immediately before it. In this use, the relative clause helps identify or specify that noun.

The grammatical role of “which” depends on the structure of the relative clause. If “which” is followed directly by a verb, “which” usually functions as the subject of the relative clause. If “which” is followed by a noun or pronoun, that noun or pronoun is the subject, and “which” functions as the object of the verb in the relative clause.

Here are some example sentences with this use of “which.”

I read a book which changed my opinion.

The relative clause can be analyzed as follows:

• Subject: the relative pronoun “which,” referring to “a book”
• Verb: changed
• Object: my opinion

In this sentence, “which changed my opinion” modifies “a book.” The relative pronoun “which” functions as the subject of the relative clause, and “changed” is the verb. The clause tells us what kind of book the speaker read.

I read a book which my teacher recommended.

The relative clause can be analyzed as follows:

• Subject: “my teacher”
• Verb: “recommended”
• Object: the relative pronoun “which,” referring to “a book”

In this sentence, “which my teacher recommended” modifies “a book.” Here, “which” doesn’t function as the subject of the relative clause. Instead, it functions as the object of “recommended.” The clause tells us which book the speaker read.

“Comma + which”

When the relative pronoun “which” is used after a comma, it introduces a nonessential relative clause. This means that the clause adds extra information rather than identifying exactly which noun is being discussed.

In many cases, “comma + which” refers to the whole idea expressed in the previous clause. This is especially common when the “which” clause describes a result or consequence.

Here are some example sentences with this use of “which.”

I read the book, which changed my opinion.

The “which” clause can be analyzed as follows:

• Subject: the relative pronoun “which,” referring to the previous idea “I read the book”
• Verb: “changed”
• Object: “my opinion”

In this sentence, “which changed my opinion” does not simply modify “the book.” Instead, it refers to the previous idea: the fact that the speaker read the book. In other words, the reading experience changed the speaker’s opinion.

She missed the final train, which forced her to take a taxi.

The “which” clause can be analyzed as follows:

• Subject: the relative pronoun “which,” referring to the previous idea “She missed the final train”
• Verb: “forced”
• Object: “her”
• Object complement: “to take a taxi”

In this sentence, “which forced her to take a taxi” refers to the result of the previous clause. It was not the train itself that forced her to take a taxi. Rather, the situation of missing the train caused that result.