Colon (punctuation)
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A colon (":") is a punctuation mark, visually consisting of two equally sized dots centered on the same vertical line. Rarely, it is also called "dots".
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Grammar
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>{{cite book
| last = Serianni | first = Luca | authorlink = Luca Serianni | coauthors = Castelvecchi, Alberto | year = 1988 | title = Grammatica italiana. Italiano comune e lingua letteraria. Suoni, forme, costrutti | publisher = UTET | location = Turin | language = Italian | id = ISBN 8802041547
}}</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.
Also a colon:
- may be used to introduce 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
- separates the chapter and the verse number(s) indication in many references to religious scriptures
- John 3:14–16 (cf. chapters and verses of the Bible)
- The Qur'an, Sura 5:18
- is used as separator 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
- may occur between a title and the corresponding subtitle
Conventions and foreign languages
In Finnish, the colon can appear inside words in a manner similar to the English apostrophe, between a word (or abbreviation) and its grammatical suffixes.
Except in French, no space is put before a colon, in most European languages. Also, the ":" is usually followed by a lowercase letter (unless the uppercase is due to other reasons, such as a proper noun etc.) except in German, where an uppercase letter must be used if the colon is followed by a complete sentence or a noun<ref>In all other cases a lowercase letter should be used, though it is a common, erroneous, practice to use uppercase in every circumstance</ref>.
Trivia:
- Many readers of the Italian writer Italo Svevo are quite surprised at seeing his usage of an uppercase letter after colons. This is not the Italian convention, nor was it at the epoch of writing. Svevo, who lived in an almost bilingual environment, adopts in fact the German usage.
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>
Phonetics
A special triangular colon symbol is used in IPA to indicate a preceding long vowel. 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.
Computing
The colon character has the decimal value 58 (hexadecimal value 3A) in Unicode and ASCII character encodings.
A colon is a special character in URLs and in the path representation of several file systems.
References
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de:Doppelpunkt eo:Dupunkto es:Dos puntos fr:Deux-points he:נקודתיים lt:Dvitaškis ja:コロン (記号) pl:Dwukropek fi:Kaksoispiste sv:Kolon zh:冒号