Grammarama

Colons

The colon is a versatile symbol. One of its duties is to separate classifications of a different hierarchy, such as between the hour and minute in the time of day, the chapter and verse of a biblical reference, or the title and subtitle of a book. Another location it appears is after the greeting in a business letter. The place it’s trickiest to use, however, is in the middle of a sentence.

When you see a colon, there should be an expectation of what comes next. Not exactly what comes next, mind you, but the colon tells us that what follows is meant to directly clarify or explain the statement preceding it. The term “statement” is of interest, because while the words to the right of the colon do not have to contain an independent clause (and often won’t), the words to the left almost always should. (For more information on clauses, see this entry: "Clauses" .)


Colons frequently introduce a list:

I want you to pick up the following things at the supermarket: bread, ham, mayonnaise, and milk.
He had a burger with all the fixings: lettuce, tomato, cheese, ketchup, mustard, and pickles.
She played three sports: soccer, softball, and tennis.

Notice the complete thoughts before the colons. The following sentences would not be appropriate:

I want you to pick up: bread, ham, mayonnaise, and milk at the supermarket.
He had a burger with: lettuce, tomato, cheese, ketchup, mustard, and pickles.
The three sports she played were: soccer, softball, and tennis.

In those cases, you would simply drop the colon altogether.


Also note that you can’t use more than one colon in a sentence; the only way to “close out” a colon is terminal punctuation—a period, question mark, or exclamation point—so a colon is in effect until that point. If the words that would come between a colon and a period are instead placed in the middle of a sentence, em dashes should be used to separate them from the main train of thought:

I want you to pick up some things at the supermarket—bread, ham, mayonnaise, and milk—before coming home from work.
He had a burger with all the fixings—lettuce, tomato, cheese, ketchup, mustard, and pickles—and it was delicious.
She played three sports—soccer, softball, and tennis—all the way through high school.


The lists after colons will never be complete sentences, but in general terms, as stated before, what comes after a colon directly clarifies or explains what’s before, and it can be a complete sentence or not.

We arrived at the last destination on our itinerary: Paris, France.
Beware of the dog: it bites.
There’s only one thing left to do: run!
Remember: only you can prevent forest fires.


I did say earlier that the words preceding a colon almost always should contain an independent clause. I say this just as I would say you usually should write complete sentences and not sentence fragments. Occasionally, writing in sentence fragments can be effective. Take the following passage written three different ways:

He was a cold-blooded murderer, his weapon of choice a knife.
He was a cold-blooded murderer; his weapon of choice was a knife.
He was a cold-blooded murderer. His weapon of choice: a knife.

Doesn’t that colon in the third passage keep you in suspense and make you take notice of what comes after it? As the strongest pause in thought short of terminal punctuation, colons can be very powerful in that way, conveying a sense of gravity and importance. The following logic applies in the following instance for the same reason:

The moral of “The Tortoise and the Hare” is that slow and steady wins the race.
The moral of “The Tortoise and the Hare”: slow and steady wins the race.


As to whether to capitalize the first letter after a colon, there isn’t a universally accepted set of rules. Some say to capitalize if it begins an independent clause, others say to never capitalize, and others fall somewhere in between. Personally, I adopt the policy of not capitalizing at all unless it begins a proper name or formal quotation.