One of the most useful grammar rules on the SAT Reading and Writing section is also one of the simplest: if a piece of a sentence can be removed without changing the core meaning, it’s considered non-essential information. Once you understand how to spot it—and how to punctuate it—you can pick up easy points on test day.
What “Non-Essential” Really Means
Non-essential information is extra detail. It might give more context, describe something more fully, or add an interesting fact—but the sentence would still make sense without it.
For example:
“The novel, which was written over ten years, became a bestseller.”
If you remove the extra detail, the sentence still works:
“The novel became a bestseller.”
That’s the key test. If the sentence still makes sense after removing the middle part, that information is non-essential.
How the SAT Wants You to Punctuate It
Once you identify non-essential information, the punctuation rule is very consistent. The extra information must be set off on both sides using one of three options:
- two commas
- two dashes
- two parentheses
Here’s the same sentence written three correct ways:
Using commas:
“The novel, which was written over ten years, became a bestseller.”
Using dashes:
“The novel—which was written over ten years—became a bestseller.”
Using parentheses:
“The novel (which was written over ten years) became a bestseller.”
All three are correct because they clearly separate the extra information from the main sentence.
What the SAT Is Really Testing
The SAT isn’t testing whether you prefer commas, dashes, or parentheses. It’s testing whether you understand sentence structure.
If the information is non-essential, it must be enclosed on both sides. If it isn’t enclosed properly, the sentence is incorrect.
The Common Mistake to Watch For
The most common error is mixing punctuation or only using one side.
Incorrect:
“The novel, which was written over ten years—became a bestseller.”
Incorrect:
“The novel which was written over ten years, became a bestseller.”
In the first example, the punctuation doesn’t match. In the second, the extra information isn’t clearly separated on both sides. The SAT will often include answer choices like these to see if you’re paying attention.
A Simple Way to Check Yourself
When you see commas, dashes, or parentheses, try this quick test: mentally remove the middle portion. If the sentence still makes sense, you’re likely dealing with non-essential information—and it needs to be enclosed properly on both sides.
For example:
“The scientist, who studied climate patterns for decades, published her findings.”
Remove the middle:
“The scientist published her findings.”
Still works. That confirms both the structure and the punctuation.
A Final Thought
This is one of those rules where clarity wins every time. If you can recognize when a sentence contains extra, removable information, you can quickly eliminate incorrect punctuation choices and move on with confidence. On a timed test like the SAT, that kind of clarity isn’t just helpful—it’s a real advantage.