Like the semicolon, the colon produces a stronger pause than the comma. But while the semicolon generally separates two independent clauses, the colon separates an independent clause from words that will explain or amplify it. There are several different ways in which the colon is used. But the most important thing to remember is this: what comes before a colon must be an independent clause.
As you can see from the previous sentence, the section of the sentence before the colon--But the most important thing to remember is this--is an independent clause. It can stand on its own as a sentence. (If you don't know what an independent clause is, see Part 1, Section A of this essay).
A. Use a colon to introduce an explanation or summary, an appositive, a series, or a quotation.
The italicized sentence above is an example of a colon used to introduce an explanation. Here is another.
Lemonade has a deceptively simple recipe: squeeze lemons into water and stir.
As you can see from that example, what follows a colon may also be an independent clause. But it doesn't have to be.
An appositive is a noun or noun substitute set beside another noun or noun substitute and identifying or explaining it. For example,
David Smith, our teacher, had a sign on his back that read "Kick Me."
Our teacher is an appositive, identifying David Smith. They are different words for the same thing.
Death, the great equalizer, got them all in the end.
So how are colons used with appositives? Here are some examples.
Three times he drags me over to the bulletin board to show me his team's enviable record: five straight league titles.
She wanted only one thing from the course: an A+.
Here five straight league titles is an appositive for his team's enviable record and an A+ is an appositive for the one thing from the course she wanted.
Note again that what comes before the colon in each case is an independent clause. The same is true when a colon is used to introduce a series.
The requirements to pass this course are the following: regular attendance, timely completion of all assignments, and class participation.
A common error students make when using the colon is to put it in a sentence where what comes before it is not an independent clause.
The requirements to pass this course are: regular attendance, timely completion of all assignments, and class participation.
This is incorrect because the section of the sentence before the colon cannot stand on its own. It is not independent.
In Part 1, Section H of this essay, we learned how commas are used with quotations. A colon can also be used to introduce a quotation, but only when what comes before the colon is an independent clause. Have I conveyed the importance of this rule yet?
The teacher said it all in the first minute of the first class: "I'm tough, and I don't like whining."
She had only one thought when she saw the final exam: "Beam me up, Scotty."
B. Use a colon after the salutation in a business letter, between a title and subtitle, between divisions of time, and in biblical citations.
These are some conventional ways in which colons are used. When you're using a colon under this rule, it's obviously not necessary that what comes before the colon be a complete sentence (this is English, after all, and there's an exception to every rule). Here are some examples.
The book is called Do It or Diet: The Last Weight-Loss Guide You'll Ever Need.
Exercises for Part 3
Here are some exercises covering what you've just learned about the colon. Insert colons or other punctuation where necessary.
- Your dedicated reader requires three props a book, a light, and a comfortable chair.
- Here are the most common names of girls born after 1990 Anne, Joan, Crystal, and Linda.
- Criminals will always have a source for guns the black market.
- My mother always said "An apple a day keeps the doctor away."
- Everything pointed to one conclusion he was insane.
- Males' favorite activities are eating, watching TV, and fixing things around the house.
- Last year was a bad time for Jane she lost her cat, moved to a new town, and got the mumps.
- I was always terrified when I heard that announcement on TV "It's 630. Do you know where your children are?"