Let's talk about piece of punctuation you probably don't use every day: the colon. You may have seen colons from time to time, but they're used on the ACT and SAT much more frequently than in our daily lives. For that reason, it’s important to learn how and when to use them.
What comes before a colon?
The simplest way to tell if a colon is being used correctly is to look on the left-hand side of the colon and ask yourself one question: do I have a full sentence (i.e. an independent clause) to the left of the colon? If the answer is “yes,” then the colon is going to be correct most of the time. In fact, if you focus on what comes on the right-hand side of a colon, you are likely to get confused and make a mistake. Here’s an example:
As a child, I enjoyed playing several different sports: basketball, baseball, and tennis.
If we stopped the sentence at the colon and replaced it with a period, would we have a full sentence? Yes. This colon is used correctly.
What comes after a colon?
Now let’s discuss what commonly comes after a colon. The first thing that can appear after a colon, as we saw in the previous example, is a list.
The second thing is a description, explanation, elaboration, or definition of the clause that precedes the colon. If that category seems overly broad, it’s supposed to be. It’s very difficult to mess up a sentence based on what comes after the colon.
Here are two examples of proper colon usage that fall into this second category:
When Detective Poirot told Mrs. Wilkinson the truth about her husband, you could describe her reaction in one word: shock.
All of those years of practicing piano were done with one goal in mind: to receive an acceptance letter from Juilliard.
The third and least common use of a colon is to separate two independent clauses:
George got what he deserved: the school was justified in expelling him.
You could just as easily put a semicolon in the middle of those two independent clauses. While there are stylistic reasons that you might choose a colon over a semicolon (and vice versa), the ACT and SAT do not test your ability to choose punctuation stylistic reasons. Either a colon or a semicolon is an equally acceptable way to separate two independent clauses, and only one of them will show up as an answer choice.
Let’s quickly review. When you see a colon in the answer choices of an ACT English question or an SAT Reading & Writing section, ask yourself the following questions:
- Do I have an independent clause to the left of the colon? If so, the correct answer may include a colon. If not, eliminate the answer with the colon.
- Is there a list or another independent clause to the right? If so, the colon is correct.
- If not, is the information to the right of the colon an explanation, elaboration, description, or definition of the first independent clause? If so, the colon fits!
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