The Colon

Colon: Do's & Don'ts

Colons are the preferred punctuation in academic writing to set off a variety of elements at the end of a sentence: lists, explanations, and other descriptions of what preceded the mark. The colon can also set off lengthy quotes or other blocks of material from your main text.

A frequent question today is whether one or two spaces should be placed after a colon. The answer may vary according to the style guide used, although in these days of proportional computer fonts, one space is usually sufficient.

Student - Teacher Conference

Student: I just got this paper back, and it looks like I’m going to need some major help on a rewrite that's due next week.

Teacher: Sure. Anything in particular you're concerned about?

Student: Well, every time I tried to use a colon, I pretty much got it wrong.

Teacher: No worries. Actually, the colon is one of the easier punctuation marks to understand. Let’s take a look at your paper.

Student: Be my guest.

A Large Colon Rule

Teacher: I’ve got some good news for you. All but one of these colon mistakes comes from the single most common important rule for colons.

Student: Do tell.

Teacher: A colon can be placed only after a complete sentence.

Student: Really? I thought a colon was part of the sentence.

Teacher: Actually, the colon replaces the period when you, the writer, wish to add something after the end of the sentence. Look at this example:

The archeologists uncovered artifacts of great importance: eating utensils, animal bones, and a burial box.

Teacher: Is there a sentence before the colon?

Student: Yeah. “The archeologists uncovered artifacts of great importance.” That’s the sentence.

Teacher: How do you know that?

Student: Well, if you put a period after “importance” there would still be a complete thought.

Teacher: Exactly. “The archeologists uncovered artifacts of great importance” could stand alone as a complete sentence. So, to add a list or any other type of extra information at the end, we replace the period with a colon.

Flushing Out Colon Errors

Student: OK, that seems simple enough. But where did I go wrong?

Teacher: Let’s look at a sentence you wrote: “Even small rooftop gardens can produce beans, squash, tomatoes, and corn.” Read the words before the colon and tell me if they form a complete sentence.

Even small rooftop gardens can produce:

Student: Oops. No, it can’t stand alone as a sentence. So, what should I do—not use a colon at all?

Teacher: That would be one correct choice. Put the list of vegetables as direct objects of the verb: no colon required.

Even small rooftop gardens can produce beans, squash, tomatoes and corn.

Teacher: Your other choice would be construct a complete sentence, add a colon, then the list. What could you add to the first part to make it a complete statement?

Student: Let’s see . . . how about:

Even small rooftop gardens can produce a variety of vegetables: beans, squash, tomatoes and corn.

Teacher: Excellent! Which of the two options do you like better: with a colon or without?

Student: For this essay, with a colon. I wanted to set off the list in order to show how many different vegetables you can grow in your apartment.

Teacher: That’s an excellent reason to use a colon, and now you know how.

Eliminating Colons

Teacher: Let’s look at one more sentence from your essay that needs this colon rule applied to it.

Apartment dwellers can still enjoy gardening in places such as: balconies, rooftops, even kitchens.

Teacher: Is there a complete sentence before the colon?

Student: OK, you got me, there isn’t. But I thought you had to put some kind of punctuation after words like “such as” to introduce a list.

Teacher: That’s a common misconception. Think of it this way: the colon has the same purpose as “such as” –to introduce. So using both of them would be redundant. This same rule applies after words like “including” or “the following.” Always go back to the basic principle: Use a colon only at the end of a complete sentence.

Getting to the Bottom of Colons: Emphasis

Teacher: In addition to setting off lists like the one you wrote, colons can also be used to add emphasis to any explanation or example. Look at this sentence:

Hollywood action films are very predictable: chase scenes separated by love scenes.

Student: I see. The sentence provides a sort of introduction to what comes at the end.

Teacher: That’s a good way of putting it. A colon lets you, the writer, introduce what comes at the end. The colon creates a full-stop pause, just like a period does, so the thing that follows receives maximum emphasis. This technique can also emphasize an entire sentence. For example:

“Americans reacted to the natural catastrophe in typical fashion: Soon the Red Cross was receiving donations at a record pace.”

Teacher: Is placing the colon after “fashion” correct?

Student: I think so. The colon comes after a complete sentence, so it’s OK to be there. Also the second sentence explains what “typical fashion” is. But I have a question? Is it OK to capitalize after the colon?

Teacher: Yes, it is. If a complete sentence follows the colon, it’s your choice whether to capitalize the first word or not. Just be consistent throughout your paper.

Conventional Colons: Subtitles

Student: OK. I can do that. Anything else I should know about the colon?

Teacher: The other error that I saw in your paper had to do with the conventional uses of a colon.

Student: What are those?

Teacher: Conventional use means in special circumstances like time designations: 11:59 p.m.; or after a formal salutation: Dear Sir or Madam: In your case it’s conventional to separate a title from its subtitle with a colon. You wrote:

“Daylight in the Garden of Plenty, Apartment Cornucopias”

Teacher: That’s a great descriptive title, but unfortunately you put a comma after “Plenty.”

Student: So it should be a colon instead?

Teacher: Exactly. In formal writing, you should separate a two-part title with a colon and be sure to capitalize the first word of both.

Student: Excellent! These rules really help. I definitely see how to use the colon more effectively now.