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Course: Digital SAT Reading and Writing  > Unit 5

Lesson 7: Boundaries: Supplements
Test prep
Digital SAT Reading and Writing
SAT Grammar practice
Boundaries: Supplements
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Grammar guide: Supplements

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A guide to supplementary phrases on the SAT.

What are supplements?

Supplements are words, phrases, and relative clauses that add extra information to a sentence, often for the purpose of description or elaboration. There are two main types of supplements:
Essential elements are necessary for the sentence to function and don't require punctuation.
Nonessential elements are not necessary for the sentence to function. They must be separated from the main sentence by punctuation.
The SAT focuses on whether supplements should be separated from the rest of the sentence by punctuation, as well as what punctuation marks should be used. These conventions may be tested in Boundaries questions that you encounter on test day.

How are supplements punctuated?

There are several factors that govern how supplements should be treated within a sentence. Let's look at each in turn.

Essential or nonessential

The first question is whether a given supplement should be punctuated. Try reading the sentence without the supplemental information.
  • If the sentence no longer makes sense, then the supplement is an essential element. No punctuation should be used.
  • If the sentence still makes sense, then the supplement is nonessential. The supplement must be separated from the rest of the sentence by punctuation.

Position in the sentence

Once you determine a supplement is nonessential, you must decide how to punctuate it.
  • If the supplement begins or ends the sentence, it only requires one punctuation mark (between the supplement and the rest of the sentence).
  • If the supplement comes in the middle of the sentence, it requires punctuation on both sides.

Type of punctuation

Nonessential elements can be separated from the rest of a sentence using three different types of punctuation marks:
  • Commas (,)
  • Parentheses ()
  • Dashes (—)
In formatting supplements, these punctuation marks are basically interchangeable. However, there is one important rule: the same type of punctuation must appear before and after a nonessential element.
In other words, we don't want to be mixing different punctuation marks together.

How to identify supplements questions

When approaching boundaries questions, it's important to identify which Standard English conventions are being tested.
You may want to look for errors in supplements if
  • the choices add or remove commas, but not conjunctions
  • the choices include multiple types of punctuation, like commas and dashes
If you don't see either of these features, then the question likely doesn't deal with supplements.
Let's look at a supplements question now:
Supplements example
Luci Tapahonso is the inaugural poet laureate of the Navajo Nation. Her book Sáanii Dahataal/The Women Are Singing—a combination of fiction and memoir, poetry and ______ serves as a testament to her versatility as a writer.
Which choice completes the text so that it conforms to the conventions of Standard English?
Choose 1 answer:

Top tips

Be consistent!

SAT questions will often include just one side of a nonessential element in the underlined portion of the sentence. Be sure to check the other side of the element for consistency: the same punctuation mark should be used on both sides!

Don't worry about the difference between commas, parentheses, and dashes

While commas, parentheses, and dashes are sometimes better in particular contexts, the SAT won't test you on these minor differences. In other words, you'll never be asked to choose between two types of punctuation marks if the choices don't create other grammar errors. So don't sweat it!

Don't pair semicolons or colons!

Commas, parentheses, and dashes are the only options when separating a nonessential element from the rest of the sentence. We should never use two semicolons or colons around a nonessential element.

Your turn

Supplements
The sandhill ______ to North America, has the longest fossil history of any extant bird at ten million years.
Which choice completes the text so that it conforms to the conventions of Standard English?
Choose 1 answer:

Supplements
Saint Lucia—a sovereign island in the ______ the only country in the world named after a historical woman.
Which choice completes the text so that it conforms to the conventions of Standard English?
Choose 1 answer:

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