# Colon (punctuation)

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Colon (punctuation)
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Colon
Punctuation Word dividers General typography Currency Uncommon typography apostrophe ( ’ ' ) brackets ( [ ], ( ), { }, ⟨ ⟩ ) colon ( : ) comma ( , ) dash ( ‒, –, —, ― ) ellipsis ( …, ..., . . . ) exclamation mark ( ! ) full stop/period ( . ) guillemets ( « » ) hyphen ( ‐ ) hyphen-minus ( - ) question mark ( ? ) quotation marks ( ‘ ’, “ ”, ' ', " " ) semicolon ( ; ) slash/stroke ( / ) solidus ( ⁄ ) space ( ) ( ) ( ) (␠) (␢) (␣) interpunct ( · ) ampersand ( & ) at sign ( @ ) asterisk ( * ) backslash ( \ ) bullet ( • ) caret ( ^ ) copyright symbol ( © ) dagger ( †, ‡ ) degree ( ° ) ditto mark ( 〃 ) inverted exclamation mark ( ¡ ) inverted question mark ( ¿ ) number sign/pound/hash ( # ) numero sign ( № ) obelus ( ÷ ) ordinal indicator ( º, ª ) percent etc. ( %, ‰, ‱ ) pilcrow ( ¶ ) prime ( ′, ″, ‴ ) registered trademark ( ® ) section sign ( § ) service mark ( ℠ ) sound recording copyright ( ℗ ) tilde ( ~ ) trademark ( ™ ) underscore/understrike ( _ ) vertical/broken bar, pipe ( ¦, | ) currency (generic) ( ¤ ) currency (specific) ( ) asterism ( ⁂ ) tee ( ⊤ ) up tack ( ⊥ ) index/fist ( ☞ ) therefore sign ( ∴ ) because sign ( ∵ ) interrobang ( ‽ ) irony & sarcasm punctuation ( ⸮ ) lozenge ( ◊ ) reference mark ( ※ ) tie ( ⁀ ) diacritical marks whitespace characters non-English quotation style ( « », „ ” )

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

## Punctuation

### Usage

A colon informs the reader that what follows the mark proves, explains, or lists elements of what preceded the mark.

Luca Serianni, an Italian scholar who helped to define and develop the colon as a punctuation mark, identified four punctuational modes for it: syntactical-deductive, syntactical-descriptive, appositive, and segmental.[1] Although Serianni wrote this guide for the Italian language, his definitions apply also to English and many other languages.

#### Syntactical-deductive

The colon introduces the logical consequence, or effect, of a fact stated before.

There was only one possible explanation: The train had never arrived.

#### Syntactical-descriptive

In this sense the colon introduces a description; in particular, it makes explicit the elements of a set.

I have three sisters: Catherine, Sarah, and Mary.

The syntactical-descriptive applies to the separation of the hour, minute, and second in abbreviated measures of time.[2][3]

The concert begins at 21:45.
The rocket launched at 09:15:05.

Similarly, the syntactical-descriptive colon separates chapter and verse numbers in citations of passages in widely-studied texts, such as epic poetry, religious texts, and the plays of William Shakespeare.[3]

John 3:14–16 or John III:14–16 refers to verses 14 through 16 of chapter three of the Gospel of John.

#### Appositive

The colon introduces an appositive independent clause. In other words, the sentence after the colon is in apposition to the one before the colon.

Luruns could not speak: He was drunk.[4]

An appositive colon also separates the subtitle of a work (which is a noun phrase) from its principal title (another noun phrase).

Star Wars Episode IV: A New Hope

#### Segmental

A segmental colon, like a dash or quotation mark, introduces speech. The segmental function was once a common means of indicating an unmarked quotation on the same line. The following example is from the grammar book The King's English:

Benjamin Franklin proclaimed the virtue of frugality: A penny saved is a penny earned.

This form is still used in written dialogues, such as in a play. The colon indicates that the words following an individual's name are spoken by that individual.

### Use of capitals

Use of capitalization or lower-case after a colon varies. In British 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, many writers capitalize the word following a colon if it begins an independent clause (i.e., a complete sentence). This follows the guidelines of some modern American style guides, including those published by the Associated Press and the Modern Language Association. The Chicago Manual of Style,[5] however, requires capitalization only when the colon introduces a direct quotation or two or more complete sentences.[6]

In many European languages the colon is usually followed by a lower-case letter (unless the upper case is due to other reasons, such as a proper noun). However, usage differs from this in German, where an upper-case letter may be used only if the sentence after the colon could stand alone without the preceding sentence (otherwise one may judge freely according to the relative independency of the two assertions),[7] and in Dutch, where an upper-case letter must be used if the colon is followed by a quotation or an enumeration of complete sentences, although in all other cases a lower-case letter should be used.[8]

### Spacing

A thin space is traditionally placed before a colon and a thick space after it. In English-language modern high-volume commercial printing, no space is placed before a colon and a single space is placed after it. In French-language typing and printing, the traditional rules are preserved.

One or two spaces may be and have been used after a colon. The older convention (designed to be used by monospaced fonts) was to use two spaces after a colon. The newer convention (designed for proportional fonts) is that one space is sufficient. See also Double spacing at the end of sentences.

## History

English colon is from Latin colon (plural cola), itself from Greek κῶλον "limb, member, portion", in rhetoric or prosody especially a part or section of a sentence or a rhythmical period of an utterance. In palaeography, a colon is a clause or group of clauses written as a line. The OED cites William Blades' The life and typography of W. Caxton (1882), p. 126: "The Greek grammarians [...] called a complete sentence a period, a limb was a colon, and a clause a comma."

Use of the : symbol to mark the discontinuity of a grammatical construction, or a pause of a length intermediate between that of a semicolon and that of a period, was introduced in English orthography around 1600. John Bullokar's An English expositor (1616) glosses Colon as "A marke of a sentence not fully ended which is made with two prickes."

John Mason in An essay on elocution (1748) prescribes "A Comma Stops the Voice while we may privately tell one, a Semi Colon two; a Colon three: and a Period four."

## Diacritical usage

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 (dot) 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, and in the practical orthography of some languages which have a phonemic long/short distinction in vowels.

If the upper triangle is used without the lower one, it designates a "half-long" vowel.[9]

## Word-medial separator

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. In Swedish, it also occurs in names, for example Antonia Ax:son Johnson (Ax:son for Axelson). In Finnish it is used in loanwords and abbreviations; e.g., USA:han for the illative case of "USA". For loanwords ending orthographically in a consonant but phonetically in a vowel, the apostrophe is used instead: e.g. show'n for the genitive case of the English loan "show" or Versailles'n for the French place name Versailles.

## Abbreviation

The colon is used to abbreviate Sankt (Swedish for "Saint"), rendering it as S:t, such as in the Stockholm Metro station S:t Eriksplan. The colon was also used to mark abbreviations in early modern English.[10][11]

## Letter

The colon is also used as a grammatical tone letter in Budu in the Democratic Republic of the Congo, in Sabaot in Kenya, in some Grebo in Liberia, and in Papua New Guinea: Erima, Gizra, Go꞉bosi, Gwahatike, Kaluli, Kamula, Kasua, Kuni-Boazi, and Zimakani.[12] The Unicode character used for the tone letter (U+A789) is different from the punctuation (U+003A).

## Mathematics and logic

The colon is used in mathematics, cartography, model building and other fields to denote a ratio or a scale, as in 3:1 (pronounced “three to one”). When a ratio is reduced to a simpler form, such as 10:15 to 2:3, this may be expressed with a double colon as 10:15::2:3; this would be read "10 is to 15 as 2 is to 3". Unicode provides a distinct ratio character, Unicode U+2236 () for mathematical usage.

The notation |G:H| may also denote the index of a subgroup.

The notation ƒ:XY indicates that ƒ is a function with domain X and codomain Y.

The combination with an equal sign, $:=\,$, is used for definitions.

In mathematical logic, when using set-builder notation for describing the characterizing property of a set, it is used as an alternative to a vertical bar (which is the ISO 31-11 standard), to mean “such that”. Example:

$S = \{x \in \mathbb{R} : 1 < x < 3 \}$ (S is the set of all x in $\mathbb{R}$ (the real numbers) such that x is strictly greater than 1 and strictly smaller than 3)

In type theory and programming language theory, the colon sign after a term is used to indicate its type, sometimes as a replacement to the $\in$ symbol. Example:

$\lambda x\cdot x\ :\ A\to A$

A colon is also sometimes used to indicate a tensor contraction involving two indices, and a double colon (::) for a contraction over four indices.

## Computing

In computing, the colon character is represented by ASCII code 58, (HTML &#58;) and is located at Unicode code-point U+003A (colon). Scripts comprising wide characters, such as kanji, use a full-width equivalent, , located at Unicode code point U+FF1A (fullwidth colon).

The colon is quite often used as a special control character in URLs,[13] computer programming languages, in the path representation of several file systems (such as HFS), and in many operating systems commands. It is often used as a single post-fix delimiter, signifying a token keyword had immediately preceded it or the transition from one mode of character string interpretation to another related mode. Some applications, such as the widely used MediaWiki, utilize the colon as both a pre-fix and post-fix delimiter.

Several programming languages use the colon for various purposes. In particular, MATLAB uses the colon as a binary operator that generates vectors, as well as to select particular portions of existing matrices. A lot of programming languages, most notably Pascal, and Ada use colon immediately followed by an equality sign, := in which case the colon and the equality sign are considering to compose to an independent assignment sign, in Unicode preferably encoded as U+2254 (colon equals). In BASIC it's used as a separator between the operators in the line. In Forth, colon precedes definition of a new word. For the double colon used in computer programming, see the scope resolution operator, and class member access of C++. The colon is also used as part of the ?: conditional operator in C and other languages. In Python, which uses indentation to indicate blocks, the colon is used in statements to indicate that the next line is the start of an indented block.

Haskell uses a colon (pronounced as “cons”, short for “construct”) as an operator to add an element to the front of a list:[14]

"child" : ["woman", "man"] -- returns ["child","woman","man"]


while a double colon :: is read as "has type of" (confer scope resolution operator):[15]

("text", False) :: ([Char], Bool)


The ML languages (including Standard ML and OCaml) have the above reversed, where the double colon (::) is used to add an element to the front of a list; and the single colon (:) is used for type guards.

Goto labels are formed in a DOS batch file by preceding a label name with a colon.

In an IPv6 address colons (and one optional double colon) separate up to 8 groups of 16 bits in hexadecimal representation.[16] In a URL a colon follows the initial scheme name (like http), and separates a port number from the hostname or IP address.[13]

## Internet usage

On the Internet, a colon, or multiple colons, is sometimes used to denote an action or to emote. In this use it has the inverse function of quotation marks, denoting actions where unmarked text is assumed to be dialogue. For example:

Tom: Pluto is so small; it should not be considered a planet. It is tiny!
Mark: Oh really? ::Drops Pluto on Tom’s head:: Still think it’s small now?

Colons may also be used for sounds, e.g. ::Click::, though sounds can also be denoted by an asterisk or other punctuation marks.

Colons are also used to represent two vertically aligned eyes in some emoticons (such as :) or :-) for a smiling face), particularly in Western (English-speaking) cultures.

## References

1. ^ Serianni, Luca; Castelvecchi, Alberto (1988) (in Italian). Grammatica italiana. Italiano comune e lingua letteraria. Suoni, forme, costrutti. Turin: UTET. ISBN 88-02-04154-7.
2. ^
3. ^ a b Trask, Larry (1997). "The Colon". Guide to Punctuation. Retrieved 28 July 2011.
4. ^ Example quoted in An Educational Companion to Eats, Shoots & Leaves by Lynne Truss
5. ^ "Chicago Style Q&A: Capitalization". Chicagomanualofstyle.org. Retrieved 2011-11-08.
6. ^ "Capital Community College: Guide to Grammar and Writing". Grammar.ccc.commnet.edu. Retrieved 2011-11-08.
7. ^ Duden Newsletter vom 24.08.2001
8. ^ "Hoofdletter na dubbele punt". Taaladvies.net. Retrieved 2011-11-08.
9. ^ "The International Phonetic Alphabet". Weston Ruter. 2005. Retrieved 27 October 2011.
10. ^ Ioppolo, Grace. Dramatists and their manuscripts in the age of Shakespeare, Jonson, Middleton and Heywood. Psychology Press. p. 73.
11. ^ Mueller, Janel; Scodel, Joshua, eds (2009). Elizabeth I: translations, 1544-1589. University of Chicago Press. p. 460.
12. ^ Peter G. Constable, Lorna A. Priest, Proposal to Encode Additional Orthographic and Modifier Characters, 2006.
13. ^ a b Berners-Lee, T.; Fielding, R.; Masinter, L. (January 2005). Uniform Resource Identifier (URI): Generic Syntax IETF. STD 66, RFC 3986.
14. ^ Real World Haskell by Bryan O'Sullivan, Don Stewart, and John Goerzen
15. ^ "Learn You a Haskell for Great Good! - Types and Typeclasses". Learnyouahaskell.com. Retrieved 2011-11-08.
16. ^ Hinden, R.; Deering, S. (Februari 2006) IP Version 6 Addressing Architecture. IETF. RFC 4291.

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