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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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".
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, 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.
- Benjamin Franklin proclaimed the virtue of frugality:— A penny saved is a penny earned.
- 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
- separation when reporting time of the day (cf. ISO 8601)
- separation of a title and the corresponding subtitle
- separation of clauses in a periodic sentence
Conventions and foreign 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.
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.
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:
[S = \: 1 < \; x < \; 3 \}] [\big(]S is the set of (all and only) x in [\mathbb] such that x is greater than 1 and smaller than 3[\big)]
Phonetics
A special triangular colon symbol is used in IPA to indicate a preceding long vowel. Its form is that of two equilateral 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.
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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