A colon promises that something is about to be provided. As pictured above, it consists of one period-sized dot above another. It is different in both appearance and function from the semicolon ( ; ), which consists of a dot above a comma.
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Uses of colons
Introducing a phrase or clause
A colon may be used to introduce a phrase or clause that represents a step forward from what came before. The movement may be from a premise to a conclusion, from an introductory phrase to a main theme, from a general statement to a particular case, or from a cause to an effect. For example, these writers use colons well:
Among the many reverberations of President Obama’s election, here is one he probably never anticipated: at least 32 African-Americans are running for Congress this year as Republicans . . . [New York Times]
While law enforcement officials don’t have exhaustive details of his travels after he was naturalized, one trip in particular stands out: He left New York on June 2, 2009, on an Emirates flight to Dubai. [Wall Street Journal]
His “three ways to be influential in American politics,” he said, were: make donations to political parties, establish think tanks, and control media outlets. [New Yorker]
Non-clausal phrases that follow colons (as in the third example above) should be uncapitalized. Usage authorities differ on whether an independent clause after a colon should be capitalized. As the first two examples above show, some major publications capitalize, and some don’t. It’s always a good idea to capitalize when the colon introduces multiple sentences. When the content before and after the colon forms a single thought, capitalization is not necessary.
Introducing a list
A colon may be used to introduce a list of items—for example:
Petrie’s concerns with wind turbines can be grouped in three areas: mortality, impact on migration and impact on foraging. [Tillsonburg News]
Introducing a self-contained quotation
A colon may be used to introduce a self-contained quotation—for example:
She added: “The law enforcement work in this case was truly exemplary.” [New York Times]
A comma may also work in this case. But when it comes to introducing a longer quotation that warrants a block quote, a colon is necessary.
Formal salutation
A colon follows a salutation in formal correspondence—for example:
To whom it may concern:
Dear Mr. Roeper:
Other uses
A colon may be used between a title and subtitle (The Story of Civilization XI: The Age of Napoleon), between a biblical chapter and verse (Exodus 2:12), and between the hour and minute in time (11:15).
