SAT / ACT Grammar in Focus: Essential vs. Non-Essential Clauses

When people speak, they often stop midway through their sentences to interject little bits of parenthetical information, sometimes even whole sentences, before finishing their original thought. Such interruptions are commonly accompanied by brief pauses, and these pauses in speech provide clues to how such asides are punctuated. Punctuation, after all, is pause. Today we’re going to look at sentences with essential clauses compared to sentences with non-essential clauses, and we’ll review how to punctuate non-essential clauses that come to interrupt one’s original thought. The grammar and punctuation rules we learn today will, if applied properly, result in an increase in your SAT Writing and Language or ACT English score. Because precious SAT and ACT points are at stake, it’s important to master this topic before heading in to test day.


Essential Clauses with “That”

First, let’s look at sentences with essential clauses. These are sentences containing the word “that,” and they indicate information that is essential (that is, necessary) to the sentence. As such, essential clauses do not get punctuation.

that = no comma


Let’s have a look:

The movie that opens on Friday looks good.

The “essential clause” here is “that opens on Friday.” Notice there’s no need for punctuation!

How about another?

The puppy that Sally adopted is cute.


Again, notice the phrase “that Sally adopted” is central to the sentence’s meaning, so it’s indicated with a non-essential clause. And, once again, no punctuation is necessary.

The main take-away? There’s no need to use a comma (or ANY punctuation mark, really) with the word “that” when it indicates the presence of an essential clause, as it does in the above examples.


Non-Essential Clauses

Non-essential clauses, in contrast to essential clauses, include information that isn’t essential to the meaning of the sentence. Instead, non-essential clauses provide “extra” or “bonus” information. They can be removed from the sentence, and the sentence will still BE a sentence with its main point intact. Let’s have a look:


The movie, which opens on Friday, looks good.

The governor, who won his race in a landslide, has a high approval rating.

The United Kingdom, where the Harry Potter books take place, is a great place to visit.


Did you spot the non-essential clauses? They’re the clauses enclosed in commas in the above examples, and each of them begins with a “W” word like which, who, where, and when.


Try removing the phrases in commas from the sentences above:

The move looks good.

The governor has a high approval rating.

The United Kingdom is a great place to visit.


Notice the sentences are still intact, still grammatically correct, and still retain their central meaning. The information we trimmed away was non-essential.


How to Punctuate Non-Essential Clauses

Although we put commas around each of the non-essential clauses in the above examples, commas aren’t the only punctuation mark writers employ to denote a non-essential clause. You’ve got options. Say you’re prepared to write a non-essential clause and you’re wondering how to punctuate it. Which of the following would you choose?


Non-essential clauses, which are not essential to the sentence’s meaning and grammatical integrity, are fun to include.

Non-essential clauses–which are not essential to the sentence’s meaning and grammatical integrity–are fun to include.

Non-essential clauses (which are not essential to the sentence’s meaning and grammatical integrity) are fun to include.


If you chose the first option, congratulations! You’re correct.

If you chose the second option, well done! You’re correct as well.

And finally, if you chose the third option, hooray for you! That’s absolutely right.

Yes, that’s right: non-essential clauses can be punctuated with two commas, two dashes, or two parentheses.

One thing you’ll probably have noticed, however, is that regardless of the punctuation mark you choose to offset your non-essential clause, you’re meant to keep it consistent. A pair of commas works well, for example, but a comma and a dash or a comma and one parenthesis? Nope. Symmetry is vital.

It’s a pretty common trick they play on both the SAT and ACT to include non-essential clauses with inconsistent punctuation. Look at this sentence, for example:

Ice cream–which is absolutely delicious, isn’t very healthy.


Did you spot the error?

That’s right, the writer of the sentence above was trying to use the non-essential clause “which is absolutely delicious,” but he failed to properly punctuate it. To fix this error, he has two choices: first, he could change the comma after “delicious” to a dash to keep the non-essential clause’s punctuation consistent with the dash that introduces it; second, he could change the dash before “which” to a comma to keep the punctuation of the beginning of the non-essential clause consistent with the punctuation that marks its end. Either way, he’ll need to use TWO consistent punctuation marks.

An iron rule of thumb for the SAT and ACT grammar sections is that “WHICH gets a comma” and “THAT gets no comma.” Don’t forget that!


Appositive Phrases

Appositive phrases are pretty much definition phrases. Rather than beginning with “w” words like which and who, appositive phrases begin with “a” or “an” and offer a definition or encapsulation of a word or concept. Like non-essential clauses, appositive phrases are meant to be punctuated with two commas, two dashes, or two parentheses. Most commonly, you’ll see them punctuated with commas.


Texas, a state in America, is big.

Texas–a state in America–is big.

Texas (a state in America) is big.

Hooray for all three options!


Interrupter Words

Non-essential clauses and appositive phrases, however, aren’t the only things you’ll need to offset from your sentences with two commas, two dashes, or two parentheses. You’ll also want to offset interrupter words like however, furthermore, indeed, nevertheless, in fact, consequently, and so on.

Such interrupter words will almost ALWAYS be punctuated with commas, but it won’t ruin anyone’s life to use dashes or parentheses, though it may look odd. Here are some sentences with interrupter words:


The movie, furthermore, went on to win several Oscars.

I think, consequently, we should take a vote.

Pyramids, indeed, are quite impressive.


Notice these little transitional words and phrases are offset with commas. Just like non-essential clauses and appositive, interrupter words should be punctuated with a pair of consistent punctuation marks, very likely commas.


The take-away

Commas (or dashes or parentheses) go around things that can be removed from the sentence while still leaving the sentence as a grammatically correct sentence.

Which gets a comma; that gets no comma.

Go forth and increase your SAT and ACT scores!

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