Here is the final grammar article from my old foray into writing for Suite 101.com. Enjoy. For more such articles, see the index for January and February on the right-hand side of the blog.
The colon—two tiny dots, one on top of the other—causes enormous confusion for beginning writers. Here’s why colons are helpful and how to use them.
Most beginning writers know that colons can be used to introduce lists. However, colons can also be used in a much broader sense: to set up expectation (as the colon just did for this sentence). Colons add variety and flavor to a piece of writing; however, they must be used properly.
As with the semi-colon, there are really only two significant uses for a colon: to introduce a list and to set the reader up to expect something.
I. Introduce Lists
When using a colon to introduce a list, make sure that the word preceding the colon is a noun:
Seven students went to the ball game on Friday night: Josh, Taylor, Courtney, Nick, Nathan, Patrick, and Jasmine.
Do not use a colon if the word that would precede it is a verb:
The seven students who went to the ball game on Friday night were Josh, Taylor, Courtney, Nick, Nathan, Patrick, and Jasmine.
Note that the content of these two sentences is the same. The only difference lies in stylistic choice of the writer. Which version is correct? They both are. But only the first requires a colon.
Do Not Use a Colon with a Preposition
Beginning writers often use a colon incorrectly:
After getting off work, Steve went to: the bank, the store, and then home.
The colon adds nothing to this sentence. The preposition to shows the proper relationship of ideas; it doesn’t need any extra help.
Colons are also not needed when introductory phrases are used instead:
Steve bought several non-essential items at the store, such as magazines and lottery tickets.
Such as also conveys what needs to be said. A colon would simply get in the way.
II. Set Up Expectation
In Sin Boldly!, David R. Williams (2004) described the colon as a mark that says, “here it is”; that is, it fulfills the expectation set up in the previous part of the sentence:
The band played the last song Bill wanted to hear after Holly dumped him: “The Goodbye Girl.”
Holly said one thing about Bill always annoyed her: He spent money too freely.
When an independent clause follows the colon—as in the second example, above—the first word may be capitalized or not, depending on your preference or the style guide you are using. However, be consistent.
Where are colons needed in the following passage? (Answer appears at end of article.)
Todd is a big fan of '60s bands such as the Beatles, the Rolling Stones, the Byrds, Jefferson Airplane, and the Who. He says there is one thing he’d like to do before he dies play bass like John Entwistle.
Use a colon to set up expectation, whether in introducing a list or in using a word, phrase, or clause that answers the previous part of the sentence. However, do not use a colon if a verb, preposition, or introducing phrase (“such as”) is used instead. (Answer: Place a colon after “dies.”)
Williams, D. (2004). Sin Boldly: Dr. Dave’s Guide to Writing the College Paper, 2nd ed. New York: Basic Books.