Printable version of Making Sense of Colons (PDF).
A colon is a form of punctuation used at the end of a complete sentence to introduce a list or quotation, offer an explanation, or highlight information. It prepares the reader for the information that comes after it.
Colons and independent clauses
A colon can join two complete sentences (independent clauses) when the second clause is connected to the first in terms of content. Capitalization of the first word in the second sentence varies according to the style manual used.
e.g., Exercise improves cognitive function in one key way: It promotes the growth of new brain cells, thereby enhancing performance on memory tasks.
In the above example, the sentence after the colon (starting with "it promotes...") offers an explanation of the "key way" identified in the first sentence. It clarifies the original sentence.
Helpful tip: colons cannot be used when the writing before the colon is not an independent clause, as in the following sentence:
My favourite foods are: sushi, pizza, and nachos.
Colons and emphasis/explanation
A colon follows a complete sentence when introducing a list or quotation, offering an example or explanation, or emphasizing a point.
- Participants responded to the survey on three occasions: baseline, pre-treatment, and post-treatment.
In the above example, the list after the colon clarifies the "three occasions" mentioned before the colon.
- Mark Twain said it best: "Age is an issue of mind over matter. If you don't mind, it doesn't matter."
In the above example, Mark Twain's quotation is provided after the colon.
- Many participants indicated there was a positive outcome of exercising daily: reduced symptoms of anxiety.
In the above example, what follows the colon ("reduced symptoms of anxiety") clarifies the "positive outcome" mentioned before the colon.
Helpful tip: another common use of the colon is to separate a title from a subtitle.
e.g., Star Wars: The Force Awakens
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