StudyPebble

SAT Commas With Nonessential Clauses

The SAT asks whether a descriptive phrase should be surrounded by commas. The answer depends on whether the phrase is needed to identify what the sentence is talking about. Extra information gets commas on both sides. Identifying information gets none.

The rule

Use a pair of commas when the phrase can be deleted without changing which thing the sentence identifies, and no commas when it cannot.

Run the deletion test. Remove the phrase and read what is left. If the sentence still identifies the same specific thing, the phrase was extra and needs commas. In: my older sister, who lives in Denver, is visiting, removing the clause leaves my older sister is visiting, which still points to one person. So the commas belong.

Now the other case. In: the students who finished early left the room, removing who finished early leaves the students left the room, which describes a different and larger group. The clause is doing identifying work, so no commas are used. Adding them would say that all the students left, which changes the meaning of the sentence.

Commas of this kind come in pairs, and dropping one of them is a standard SAT error. A sentence reading: the report, which arrived Tuesday was incomplete, is wrong because the interruption opens with a comma and never closes. Whenever you see one comma around a descriptive phrase, check for its partner.

Dashes and commas follow the same logic and must match each other. If a nonessential phrase opens with a dash, it closes with a dash, not a comma. Mixing the two marks around a single interruption is another error the test likes, and the fix is simply to make the pair consistent.

A related rule covers appositives, which are noun phrases that rename something. In: the novelist, a former engineer, wrote about bridges, the middle phrase is extra and takes commas. But in: the novelist Jane Ellis wrote about bridges, the name is identifying which novelist, so no commas appear. Same structure, different job, opposite punctuation.

The trap

Opening a nonessential phrase with a comma and forgetting to close it with the matching comma.

Try it

Try one
Real question

Which choice completes the text so that it conforms to the conventions of Standard English? The book that was published last year ______ received strong reviews.

The clause in the 1878 ______ that gives the town the right to draw water from the river above the mill is the clause every lawyer in the case has spent the last four years reading in a slightly different way from all the others.

Which choice completes the text so that it conforms to the conventions of Standard English?

  • A) charter ✓
  • B) charter;
  • C) charter —
  • D) charter,

Why: The "that" clause identifies which clause of the charter is meant, so it is essential and takes no punctuation before it. "charter," would mark it as extra information that could be removed, and removing it leaves the sentence claiming that some unspecified clause is the one the lawyers dispute. "charter;" is wrong because a semicolon requires an independent clause on each side, and the words before the blank are not one. "charter —" sets off with a dash a clause that is essential to identifying the subject, which has the same wrong effect as a comma would.

Practice more of these free

Questions students ask

What is the difference between which and that?

In careful usage, which introduces a nonessential clause and takes a comma, while that introduces an essential clause and takes none. On the SAT, focus on the comma question, since the punctuation is what the answer choices usually vary.

Can I use a dash instead of the commas?

Yes, as long as both ends of the interruption use the same mark. A phrase opened with a dash must close with a dash, and a phrase opened with a comma must close with a comma. Mixing them is an error even when each mark would be acceptable alone.

Guides that cover this