The colon may be used between two independent clauses not joined by a conjunction if the second clause explains, illustrates or enlarges upon the first. In such sentences a semicolon would also be correct, but less effective:
A colon may be used between two clauses in antithesis:
The work of the colon could have been done by a period or even a comma in the above example.
The colon is used primarily to introduce the words that follow it. It introduces a formal quotation or a formal statement:
Short quotations or declarations, however, are usually introduced by a comma (see 7.18 Quotations, etc.).
The colon is also used for the question-and-answer format, to introduce dialogue and in transcriptions:
The colon introduces a list, but should not be used after "such as," "for instance" or "for example," or if the list is the object or complement of an element in the annunciatory statement:
In cases such as the last two, use no punctuation after the annunciatory statement or insert a phrase such as "the following," "as follows" or "as illustrated," which then takes a colon.
The colon can be used to introduce vertical lists, even if the series is a complement or object:
The teleworking issues before the working group included:
However, here too, an introductory phrase ("the following," etc.) is preferable.
In business letters and printed speeches, a colon follows the salutation:
In personal letters, the colon is usually replaced by a comma:
The colon is used to separate titles from subtitles. It is followed by a single space:
In references to books, plays, etc., colons separate chapter and verse, volume and page and act and scene, with no space on either side of the colon:
Location and name of publisher are also separated by a colon. The colon is followed by a single space:
See Chapter 9 Reference Matter for further information on the use of the colon in reference matter.
See Chapter 5 Numerical Expressions for uses of the colon with numerical expressions.
Do not use a colon followed by a dash (:—).
Do not place a colon at the end of a title or heading standing on a separate line from the text it introduces.
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