Commas and subordinate clauses

Subordinate (dependent) clauses have a subject and a verb, but they can’t stand alone as sentences because they begin with a subordinating word such as although, because, which, that, or who. Whether a subordinate clause, or a shorter modifying phrase, needs commas depends on where it sits and whether it is essential to the meaning. This chapter covers three cases: introductory elements, non-essential elements, and which/that/who clauses.

Introductory elements

An introductory element can be a single word, a phrase, or a full clause. Put a comma after an introductory clause and after most introductory words and phrases; only a very short phrase (In 2010 she moved) can go without one.

Although it was a sunny day with clear blue skies and not a cloud in sight, Vladimir carried an umbrella.

Additionally, he wore his boots.

Be cautious about commas within introductory elements. They are sometimes necessary to separate coordinate adjectives or items in lists, but they are not used to punctuate a series of prepositional phrases. A misplaced comma can unintentionally change the meaning of a sentence.

INCORRECT: Although it was a sunny day, with clear blue skies, and not a cloud in sight, Vladimir carried an umbrella.

CORRECT: Although it was a sunny day with clear blue skies and not a cloud in sight, Vladimir carried an umbrella.

Here, the commas after day and skies surround the prepositional phrase with clear blue skies, breaking up the image the clause is establishing. The extra commas chop one continuous clause into pieces; the only comma needed is the one after the entire introductory clause.

Practice question

Although driving across the country with our six-member family in Granny’s tiny Honda Civic sounded like a nightmare, I had to admit that it had a certain appeal as well.

Choose the correct answer:

a. NO CHANGE
b. Although driving across the country, with our six-member family in Granny’s tiny Honda Civic sounded like a nightmare, I had to admit that it had a certain appeal as well.
c. Although driving across the country with our six-member family, in Granny’s tiny Honda Civic sounded like a nightmare, I had to admit that it had a certain appeal as well.
d. Although, driving across the country with our six-member family in Granny’s tiny Honda Civic sounded like a nightmare, I had to admit that it had a certain appeal as well.
e. Although driving across the country with our six-member family in Granny’s tiny Honda Civic sounded like a nightmare I had to admit that it had a certain appeal as well.

Correct answer:

Non-essential elements

Non-essential elements are often difficult for students to spot because they sit in the middle of sentences that may also include multiple adjectives or lists.

Non-essential elements add detail to sentences, but they are not grammatically essential for the sentence to make sense. Compare the following two sentences:

Stellaluna is a perennial favorite among my second graders.

Stellaluna, a children’s story about a fruit bat, is a perennial favorite among my second graders.

Both sentences are grammatically correct. The non-essential phrase (an appositive), a children’s story about a fruit bat, adds detail to the second sentence, but it is not grammatically necessary. Without it, the sentence still makes sense.

Here is another example. This one uses a non-essential element known as an interrupter—a name in direct address.

It is important, Roberta, not to give personal information to strangers who call you on the phone.

Here, the name Roberta interrupts the statement, It is important not to give personal information to strangers who call you on the phone. The addition of Roberta, which is surrounded by commas like any non-essential element, adds detail by clarifying who is being addressed, but it is not grammatically necessary.

A concluding modifier is a word, phrase, or clause at the end of a sentence that comments on the rest of it or adds a contrasting, nonessential idea. It is separated from the rest of the sentence with a comma.

The trip was not cancelled, thank goodness.

The media overestimated the amount of snowfall we would get, predictably.

Very few people use pumpkins for food today, although that was not always true.

In each of the above sentences, a comma separates the main clause from a concluding modifier, whether the modifier is one word or a lengthy phrase. Not every clause at the end of a sentence takes one, though. A clause that says why, when, or on what condition the main action happens (so that, because, until, if) is essential to the meaning and usually takes no comma, as the next question shows.

Practice question

Bill likes to leave the butter out on the table, so that it will be soft enough to spread on his bagel in the morning. Bob, in contrast, thinks the warm butter is rancid and dangerous to eat.

Choose the correct answer:

a. NO CHANGE
b. Bill likes to leave the butter out, on the table so that it will be soft enough to spread on his bagel in the morning. Bob, in contrast, thinks the warm butter is rancid and dangerous to eat.
c. Bill likes to leave the butter out on the table so that it will be soft enough to spread on his bagel in the morning. Bob, in contrast, thinks the warm butter is rancid and dangerous to eat.
d. Bill likes to leave the butter out on the table so that it will be soft enough to spread on his bagel in the morning, Bob, in contrast, thinks the warm butter is rancid and dangerous to eat.
e. Bill likes to leave the butter out on the table so that it will be soft enough to spread on his bagel in the morning. Bob, in contrast, thinks the warm butter is rancid, and dangerous to eat.

Correct answer:

Which/that/who

• Which usually indicates that the information coming up is non-essential and can be removed from the sentence without damaging its grammar or meaning. A non-essential which clause is set off with commas. (After a preposition, which can begin an essential clause with no comma: the house in which she grew up.)
• That indicates that upcoming information is essential to the meaning of the sentence. Clauses that begin with that are not preceded by commas.
• Who can indicate either kind of clause, depending on the context in which it is used. Comma use must be adjusted according to the structure of each sentence. The next chapter, Commas with adjectives and which/that/who clauses, walks through examples of both kinds of who clauses.

Let’s start with a which clause.

All of the books, which Beth had read, were extremely interesting.

Here, we have a pile of interesting books. It just so happens that Beth has read them, but that detail is non-essential to the meaning and grammar of the sentence’s main clause:

All of the books were extremely interesting.

If the sentence uses that instead of which, the sentence’s meaning changes:

All of the books that Beth had read were extremely interesting.

Now the sentence is about only the books Beth had read, and it says nothing about any other books. The that clause tells us which books are meant, so it is essential.

Practice question

The birds that had built their nests in Diane’s front-door wreath made it impossible to use the front door for eight weeks every spring.

Choose the correct answer:

a. NO CHANGE
b. The birds, which had built their nests in Diane’s front-door wreath, made it impossible to use the front door for eight weeks every spring.
c. The birds which had built their nests in Diane’s front-door wreath made it impossible to use the front door for eight weeks every spring.
d. The birds that had built their nests, in Diane’s front-door wreath, made it impossible to use the front door for eight weeks every spring.
e. The birds, that had built their nests in Diane’s front-door wreath, made it impossible to use the front door for eight weeks every spring.

Correct answer: