Colon (punctuation)
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- This article is about colons in punctuation. For other uses of similar terms, see Colon (disambiguation) and Colón.
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The colon (":") is a punctuation mark, visually consisting of two equally sized dots centered on the same vertical line. Rarely, it is also called snake eyes (slang) or "dots".<ref>The Secret Guide to Computers</ref>
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[edit] Grammar
[edit] Usage
As with many other punctuation marks, the usage of colon varies among languages and, for a given language, among historical periods. As a rule of thumb, however, a colon informs the reader that what follows proves, clarifies, explains, or simply enumerates elements of what is referred to before.
The following classification of the functions that a colon may have, given by Luca Serianni for Italian usage,<ref>Serianni, Luca, Castelvecchi, Alberto (1988). Grammatica italiana. Italiano comune e lingua letteraria. Suoni, forme, costrutti (in Italian). Turin: UTET. ISBN 88-02-04154-7.</ref> 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, explicits 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.
This last was once a common means of indicating an unmarked quotation on the same line (from the Fowlers' grammar book, The King's English)
- Benjamin Franklin proclaimed the virtue of frugality:— A penny saved is a penny earned.
A colon may also be used for the following:
- introduction of a definition
- A: the first letter in the Latin alphabet
- Hypernym of a word: a word having a wider meaning than the given one; e.g. vehicle is a hypernym of car
- 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
- John 3:14–16 (or John iii:14–16) (cf. chapters and verses of the Bible)
- The Qur'an, Sura 5:18
- separation when reporting time of the day (cf. ISO 8601)
- The concert finished at 23:45
- This file was last modified today at 11:15:05
- separation of a title and the corresponding subtitle
- separation of clauses in a periodic sentence
In English, a colon may be followed either by a capital letter or by a lower case letter, as the author prefers (unless a capital letter is necessary for a proper noun). No particular consistency is required within a given text, although it is assumed that use of both capital letters and lower case letters after colons, in a single given text, would serve some purpose in communicating the author's desired meaning, rather than simply reflecting carelessness.
[edit] Conventions and non-English languages
In European languages the colon is usually followed by a lowercase letter (again, unless the uppercase is due to other reasons, such as a proper noun). An exception is German, where an uppercase letter must be used if the colon is followed by a complete sentence or a noun, although in all other cases a lowercase letter should be used.
No space is put before a colon, except in French.<ref>Lexique des règles typographiques en usage à l'Imprimerie nationale, ISBN 2-7433-0482-0</ref>
In Finnish and Swedish, the colon can appear inside words in a manner similar to the English apostrophe, between a word (or abbreviation, especially an acronym) and its grammatical (mostly genitive) suffixes.
[edit] Mathematics
The colon is also used in mathematics, cartography, model building and other fields to denote a ratio or a scale, as in 3:1 (pronounced "three to one"). Unicode provides a distinct ratio character, Unicode U+2236 (∶) for mathematical usage.
In logic and, correspondingly, when describing the characterizing property of a set, it is used as an alternative to a vertical bar, to mean "such that". Example:
<math>S = \{x \in\mathbb{R}: 1 < \; x < \; 3 \}</math> <math>\big(</math>S is the set of (all and only) x in <math>\mathbb{R}</math> such that x is greater than 1 and smaller than 3<math>\big)</math>
In the non-English speaking countries the colon is used as division sign - "a divided by b" is written as a : b.
The combination with an equal sign, <math>:=\,</math>, is used for definitions.
[edit] Phonetics
A special triangular colon symbol is used in IPA to indicate that the preceding sound is long. Its form is that of two triangles, each a bit larger than a point of a standard colon, pointing toward each other. It is available in Unicode as modifier letter triangular colon, Unicode U+02D0 (ː). A regular colon is often used as a fallback when this character is not available.
[edit] Computing
In computing, the colon character is represented by ASCII code 58, and is located at Unicode code-point U+003A. The full-width (double-byte) equivalent, ：, is located at Unicode code point U+FF1A.
The colon is a special character in URLs, computer programming languages, and in the path representation of several file systems.
[edit] References
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de:Doppelpunkt es:Dos puntos eo:Dupunkto eu:Bi puntu (ikurra) fr:Deux-points hr:Dvotočje it:Due punti he:נקודתיים lt:Dvitaškis nl:Dubbele punt ja:コロン (記号) no:Kolon pl:Dwukropek pt:Dois pontos ru:Двоеточие sh:Dvotočka fi:Kaksoispiste sv:Kolon zh:冒号
