On the Digital SAT, within-sentence punctuation questions ask you to correctly punctuate the interior of a sentence. While a related topic (Boundaries: Between Sentences) covers how to join or separate independent clauses, this topic focuses on what happens inside a sentence: coordinating elements in a series, setting off supplementary information like appositives and parentheticals, using conjunctive adverbs and colons correctly within sentences, and knowing when no punctuation is needed at all. You'll see roughly 3–5 questions on these skills, and they all use the same stem: "Which choice completes the text so that it conforms to the conventions of Standard English?"
Coordinating Elements in a Series
When a sentence lists three or more items, those items need to be separated by commas. The SAT uses the Oxford comma (the comma before "and" in a list), so always include it.
Example passage:
The conservator carefully cleaned ______ and documented each artifact before returning it to storage.
- A) cataloged, photographed,
- B) cataloged, photographed
- C) cataloged photographed
- D) cataloged photographed,
The correct answer is A. You have a series of three verbs: cleaned, cataloged, photographed, and documented. Each item in the series needs a comma after it, including the one right before "and."
The rule is straightforward: for a series of three or more parallel elements, place commas between every item. If there are only two items joined by "and," no comma is needed between them. The SAT tests whether you can tell the difference between a two-item compound and a true series.
Semicolons in a Complex Series
When the items in a series already contain commas, you use semicolons to separate the larger items. This prevents confusion about where one item ends and the next begins.
Example passage:
The research team included Dr. Yuki Tanaka, a marine ______ Dr. Amir Patel, a statistician from Mumbai; and Clara Reyes, a field ecologist based in Costa Rica.
- A) biologist from Osaka
- B) biologist from Osaka;
- C) biologist, from Osaka;
- D) biologist from Osaka,
The correct answer is B. Each item in this series is a name followed by a descriptive phrase containing a comma ("a marine biologist from Osaka"). Because the items themselves have internal commas, semicolons must separate the items from each other.
Coordinating Clauses and Conjunctive Adverbs
When two independent clauses are joined within a single sentence, the punctuation depends on what word connects them. Coordinating conjunctions (FANBOYS: for, and, nor, but, or, yet, so) take a comma before them. But conjunctive adverbs like however, therefore, moreover, consequently, furthermore, and nevertheless follow different rules.
A conjunctive adverb between two independent clauses requires a semicolon before it and a comma after it:
The initial results were promising; however, subsequent trials failed to replicate them.
The SAT loves to test whether you know that however and similar words are not coordinating conjunctions. You cannot write: The results were promising, however, subsequent trials failed. That's a comma splice.
Example passage:
Astronomers had long theorized about the existence of exoplanets orbiting distant ______ it was not until 1992 that the first confirmed detection was made.
- A) stars, however,
- B) stars however
- C) stars; however,
- D) stars, however
The correct answer is C. Two independent clauses are connected by the conjunctive adverb "however." The semicolon goes before "however," and a comma follows it.
Colons Within Sentences
A colon can introduce a list, an explanation, or a specification, but only when what comes before the colon is an independent clause. What comes after the colon does not need to be an independent clause.
Example passage:
Since then, marine biologists have identified two living ______ the West Indian Ocean coelacanth and the Indonesian coelacanth.
- A) species,
- B) species:
- C) species;
- D) species
The correct answer is B. The clause before the colon ("marine biologists have identified two living species") is a complete thought, and what follows specifies which two species. The colon signals "here's what those species are." A semicolon would be wrong because "the West Indian Ocean coelacanth and the Indonesian coelacanth" is not an independent clause.
Incorporating Supplementary Information
Appositives and parentheticals are pieces of supplementary information inserted into a sentence. An appositive renames or identifies a nearby noun. A parenthetical adds extra detail that could be removed without breaking the sentence's grammar. Both must be set off with punctuation, and the punctuation must match on both sides.
You have three options for setting off supplementary information:
- Commas: The most common choice. Frida Kahlo, a Mexican painter, is celebrated worldwide.
- Dashes: Slightly more emphatic. Frida Kahlo—a Mexican painter—is celebrated worldwide.
- Parentheses: De-emphasizes the information. Frida Kahlo (a Mexican painter) is celebrated worldwide.
The critical rule: the opening and closing punctuation must match. If you open with a comma, you must close with a comma. If you open with a dash, you close with a dash. The SAT frequently offers mismatched pairs as wrong answers.
Example passage:
Architect Maya Lin, who designed the Vietnam Veterans Memorial in Washington, D.C., at the age of twenty-one, ______ known for creating works that merge art and landscape architecture.
- A) is also
- B) , is also
- C) —is also
- D) ; is also
The correct answer is A. The phrase "who designed the Vietnam Veterans Memorial in Washington, D.C., at the age of twenty-one" is a nonessential relative clause set off by commas. The opening comma appears after "Lin" and the closing comma appears after "twenty-one." After that closing comma, the main clause resumes with the verb "is also." No additional punctuation is needed before the verb.
How to Spot Supplementary Information
Ask yourself: can this phrase be removed without making the sentence grammatically incomplete? If yes, it's supplementary and needs to be set off. If removing it breaks the sentence, it's essential and should not be set off.
Compare:
- The novelist Toni Morrison won the Nobel Prize. (No commas. "Toni Morrison" is essential to identifying which novelist.)
- Morrison, a Nobel laureate, wrote eleven novels. (Commas. "A Nobel laureate" is extra information about Morrison, who is already identified by name.)
When No Punctuation Is Needed
This is where many students over-punctuate. The SAT tests whether you know that certain sentence elements should NOT be separated by punctuation.
Never place a comma between:
- A subject and its verb, no matter how long the subject is. The politician who campaigned across all fifty states [no comma] won the election.
- A verb and its direct object. The researchers discovered [no comma] a new species of frog.
- A preposition and its object. The award was given to [no comma] the youngest competitor.
- Two items joined by a single conjunction. She studied biology and chemistry [no comma needed with only two items].
Example passage:
The documentary filmmaker whose work has been featured at Sundance and Cannes ______ currently developing a series about coral reef restoration in the Pacific.
- A) , is
- B) is
- C) , is,
- D) ; is
The correct answer is B. "The documentary filmmaker whose work has been featured at Sundance and Cannes" is the complete subject. No punctuation should separate it from the verb "is." Choice A incorrectly inserts a comma between subject and verb. Choice D incorrectly uses a semicolon, which requires independent clauses on both sides.
The SAT counts on long, complex subjects making you feel like a comma "should" go somewhere. Resist that urge. If the words before the verb are all part of the subject, no comma belongs there.
What to Watch For on Test Day
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Match your punctuation pairs. When supplementary information is set off mid-sentence, check that the opening and closing marks are the same type (both commas, both dashes, or both parentheses). Mismatched pairs are a favorite trap.
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Don't confuse conjunctive adverbs with coordinating conjunctions. Words like however, therefore, moreover, and consequently need a semicolon before them when they sit between two independent clauses. A comma alone won't work.
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Long subjects don't earn commas. No matter how many words pile up before the verb, if they're all part of the subject, don't put a comma before the verb. Read the sentence without the modifying phrases to confirm the subject-verb connection.
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Check what comes before a colon. A colon requires an independent clause on its left side. If the words before the colon don't form a complete sentence, the colon is wrong.
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Count your list items. Three or more items in a series need commas (or semicolons if the items contain internal commas). Two items joined by "and" don't need a comma between them.