Colon (punctuation)

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The colon (:) is a punctuation mark consisting of two equally sized dots centered on the same vertical line.

As with many other punctuation marks, the usage of colon varies among languages and, within a given language, across historical periods. As a rule, however, a colon informs the reader that the following proves, explains or simply provides elements of what is referred to before.

The following classification of the functions that a colon may have, given by Luca Serianni (a pioneer of the colon) for Italian usage,[1] is generally valid for English and many other languages:

  • syntactical-deductive: introduces the logical consequence, or effect, of a fact stated before
  • syntactical-descriptive: introduces a description—in particular, makes explicit the elements of a set
  • appositive: introduces a sentence with the role of apposition with respect to the previous one
  • segmental: introduces a direct speech, in combination with quotation marks and dashes. The segmental function was once a common means of indicating an unmarked quotation on the same line. The following example is from Fowler's grammar book, The King’s English:

A colon may also be used for the following:

  • introduction of a definition
  • separation of the chapter and the verse number(s) indication in many references to religious scriptures, and also epic poems; it was also used for chapter numbers in roman numerals
  • separation of hours, minutes and seconds when reporting the time of day (cf. ISO 8601; alternatively, a period (.) may be used[3])
  • separation of a title and the corresponding subtitle


Use of capitals

In English, the word following the colon is in lower case unless it is a proper noun or an acronym, or if it is normally capitalized for some other reason. However, in American English a colon may be followed either by a capital letter or by a lower-case letter, depending on usage: where direct speech follows, a capital letter is used; where an acronym or proper noun follows, a capital is used; otherwise, a lower-case letter is used.[3] Some modern American style guides, including those published by the Associated Press and the Modern Language Association, prescribe capitalization where the colon is followed by an independent clause (i.e. a complete sentence). However, The Chicago Manual of Style[4] requires capitalization only when the colon introduces two or more complete sentences.[5]

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