Some uses of the colon are purely conventional--after the greeting in business letters (Dear Mr. Johnson:), between the hour and minute in expressions of time (2:30 a.m.), between a title and subtitle (George Washington: A Man of His Time), and between book and verse numbers in biblical citations (I Corinthians:2-5)—and those uses will not be discussed in this handout. But other uses of the colon have a grammatical purpose, and since those uses are the ones that are most often misunderstood, they are the ones we will consider.
Colons (:) can be used as sentence connectors in several ways: to introduce lists
or series, including bulleted lists; to introduce quotations, including block quotations;
and, in special circumstances, to join two sentences to create a compound sentence.
The main rule for correctly punctuating with colons is to make sure that what comes before the colon is a complete grammatical construction (usually a complete sentence). To test whether you have used a colon correctly or incorrectly, delete the information after the colon to see if what is left is a sentence that can stand alone. If the information does stand alone, then you have used the colon correctly. If the information that comes before the colon cannot stand alone, then you shouldn’t use a colon there.
Let’s look at a sentence that uses the colon correctly.
Ex.: Three things are most important for a five-year-old child: Mommy Daddy, and home.
In this sentence, when we delete the information after the colon (Mommy, Daddy, and home), we are left with a clause that could be a complete sentence (Three things are most important for a five-year-old child). We could put a period after child, and everyone would understand the statement as a sentence.
Now let’s look at a sentence that uses the colon incorrectly.
Ex.: The three most important things for a five-year-old child are: Mommy, Daddy, and home.
In this example, when we delete the information after the colon (Mommy, Daddy, and home.) we see that what is left (The three most important things for a five-year-old are) cannot stand alone; we could not put a period after are, so we should not use a colon there.
Using Colons to Introduce Series and Lists
We often use colons to set up lists or series of items when we want to emphasize the list or series for some reason. We use the colon in such cases to point to the information that comes after it. Most often the list is an appositive that renames or defines some part of the information that comes before the colon, and the information can be presented as either a horizontal list or as a vertical list. But the main rule for using colons still applies: the information that comes before the colon must be a complete sentence.
Let’s look at an example.
Ex.: Susan plans on bringing several crucial items to the picnic: cokes, napkins, plates and forks.
In the example above, the horizontal list following the colon is an appositive that more specifically defines the items that Susan will bring to the picnic. Please note that we could put a period after picnic, and the sentence would still make sense.
Now let’s look at the same information in a sentence that is punctuated incorrectly.
Ex.: Susan plans on bringing: cokes, napkins, forks and plates.
The example above illustrates an incorrect use of the colon. If the list is deleted, the sentence no longer makes sense and the remaining information (Susan plans on bringing) is a fragment.
The same rule applies when you use colons to set up vertical lists, including numbered or bulleted lists: the information before the colon must be a complete sentence.
Ex.: The AMA has identified four major symptoms of drug abuse:
- Red eyes,
- Problems with comprehension,
- Withdrawal from social interaction, and
(Please note that capitalizing the first word in each item of a bulleted list is optional—though capitalizing perhaps provides more emphasis. Also note that the comma between items is considered optional in most business and technical writing.)
Using Colons to Introduce Quotations
If you haven’t already noticed the pattern, let me say again, when you use a colon to introduce a quotation, the information that comes before the colon must be a complete sentence.
Ex.: Frederick expresses his concern about heart disease: “Deaths from heart disease in America will increase five-fold in the next twenty years.”
Here’s a hint about introducing a quotation with a sentence and a colon: the information before the colon should add to the reader’s understanding of the quotation—it should set up a context for or explain something about the quote. This hint becomes even more important when you are setting up a block quotation.
Ex.: In The Power of Myth, a conversation about mythology, Joseph Campbell enlightens Bill Moyers about how a dream differs from a myth: “Oh, because a dream is a personal experience of that deep, dark ground that is the support of our conscious lives, and a myth is society’s dream" (40).
Using Colons to Create Compound Sentences
We all know that we can use a semicolon to join two sentences to create a compound
sentence when the two sentences are closely related. But when the first sentence
of the pair creates an expectation in the reader that the second sentence fulfills,
then the correct punctuation to use to connect them is a colon. In other words the
second sentence illustrates, explains or exemplifies the idea expressed in the first
Ex.: The adoption of a totem implies an awareness of a disunity where there once was unity: the conscious human decision to adopt the totem must have arisen from a sense of loss or absence and the desire to bridge the chasm.
Please note, you have the option of capitalizing the first word after the colon in this kind of compound sentence.
You can test your understanding of this handout by completing Academic Center exercises available here.
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