SAT® punctuation: comma, semicolon or colon — how do I choose?
With one test: cover each side of the punctuation mark and ask whether it could stand alone as a complete sentence. Most comma, semicolon and colon questions on the SAT are decided by that test, and most wrong answers come from choosing by how the punctuation looks instead.
The test, and what it tells you
Both sides are complete sentences. You need a period or a semicolon (or a comma with a word like and or but). A comma alone is not enough to join two sentences.
The left side is a complete sentence and the right side explains, lists or names something. A colon works. What comes after a colon does not need to be a full sentence, but what comes before it does.
One side is not a complete sentence. A semicolon is wrong. Usually a comma, or no punctuation at all, is what the sentence needs.
That is the whole method for most of these questions. It does not require knowing the names of grammatical structures, only asking the same question about each side.
One example
The sentence: “After three years of testing ______ the engineers finally approved the design.” The choices include a semicolon and a comma.
What happens: the semicolon looks more serious, and the pause feels long, so you choose it. Cover the right side and read the left: “After three years of testing.” That is not a sentence. A semicolon needs a complete sentence on both sides, so it is wrong. The comma is correct.
This is the most common mistake in these questions: choosing a semicolon because the pause feels important, when one side cannot stand alone.
Two more things to check
No punctuation between a subject and its verb, or a verb and its object. “The results of the long and careful study, showed…” is wrong: the comma splits the subject from its verb. Some of the choices will add punctuation that looks natural but breaks the sentence in the middle.
Pairs of commas. If an extra piece of information is set off by a comma on one side, it needs the same mark on the other side. When one comma is missing, the choice with the matching mark is usually right.
How to practise
Do twenty of these questions and, for each one, say the test out loud: “left side, sentence or not? Right side, sentence or not?”. It feels slow at first. After a week it takes two seconds, and you will stop choosing by the look of the mark.
This happens to a lot of people. What you don't know yet is whether it happens to you, and with which one. Sixteen questions will tell you.
Try the sixteen free questions
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