SAT Commas Rules
By the Cheetah Prep team
The SAT tests commas for four specific jobs and nothing else: before a FANBOYS conjunction joining two sentences, after an introductory element, around removable information, and between items in a list. If a comma is not doing one of those four jobs, it probably does not belong.
The most common comma error on the test is the opposite problem, a comma that should not be there. The classic trap is a single comma dropped between a long subject and its verb. When you see a comma, ask which of the four jobs it is doing. If the answer is none, cut it.
The Commas Rules the SAT Tests
Comma before FANBOYS joining two sentences
When for, and, nor, but, or, yet, or so joins two complete sentences, put a comma before it.
The river rose overnight and the town issued a warning.
The river rose overnight, and the town issued a warning.
On the SAT: Watch for a comma dropped before the conjunction, or added before a conjunction that only joins two words.
Comma after an introductory element
A word, phrase, or dependent clause that opens a sentence is followed by a comma.
After finishing the final round of edits the author sent the manuscript.
After finishing the final round of edits, the author sent the manuscript.
On the SAT: Frequently tested with long introductory phrases where the comma is missing or misplaced.
Commas around nonessential information
Information that can be removed without changing the core meaning gets a pair of commas, one before and one after.
The novelist, who won the prize last year released a sequel.
The novelist, who won the prize last year, released a sequel.
On the SAT: The SAT tests whether you use a matched pair, not just one, and whether the element is actually removable.
No comma between a subject and its verb
Never separate a subject from its verb with a single comma, no matter how long the subject is.
The students who studied every night for a month, passed easily.
The students who studied every night for a month passed easily.
On the SAT: A favorite trap: a long subject followed by a stray comma right before the verb.
No comma before an essential clause
A clause the sentence needs to identify its subject (often starting with that) takes no comma.
The bill, that the senate passed, takes effect in June.
The bill that the senate passed takes effect in June.
On the SAT: The SAT contrasts essential and nonessential clauses; adding a comma to an essential one is wrong.
Drill Commas on Real Questions
Knowing a rule and spotting it under time pressure are different skills. The diagnostic shows whether commas is costing you points, and Cheetah Prep drills each rule in real digital SAT questions until you catch the pattern on sight.
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