This article is about the punctuation mark. For a colon-like character used as an alphabetic letter in some languages, rather than as punctuation, seeColon (letter). For other uses, seeColon (disambiguation).
Colon (punctuation)
Thecolon,:, is apunctuation mark consisting of two equally sized dots aligned vertically. A colon often precedes an explanation, a list,[1] or a quoted sentence.[2] It is also used between hours and minutes in time,[1] between certain elements inmedical journal citations,[3] betweenchapter and verse inBible citations,[4] between a two numbers in aratio, and, in the US, forsalutations in business letters and other formal letters.[1]
In 1589, inThe Arte of English Poesie, theEnglish termcolon and the corresponding punctuation mark: is attested:[7][a]
For these respectes the auncient reformers of language, inuented, three maner of pauses [...] The shortest pause or intermission they calledcomma [...] The second they calledcolon, not a peece but as it were a member for his larger length, because it occupied twise as much time as the comma. The third they calledperiodus, [...]
As late as the 18th century,John Mason related the appropriateness of a colon to the length of the pause taken when reading the text aloud, butsilent reading eventually replaced this with other considerations.[12]
In modern English usage, a complete sentence precedes a colon, while a list, description, explanation, or definition follows it. The elements which follow the colon may or may not be a complete sentence: since the colon is preceded by a sentence, it is a complete sentence whether what follows the colon is another sentence or not. While it is acceptable to capitalise the first letter after the colon in American English, it is not the case in British English, except where a proper noun immediately follows a colon.[13]
Colon used before list
Daequan was so hungry that he ate everything in the house: chips, cold pizza, pretzels and dip, hot dogs, peanut butter, and candy.
Colon used before a description
Bertha is so desperate that she'll date anyone, even William: he's uglier than a squashed toad on the highway, and that's on his good days.
Colon before definition
For years while I was reading Shakespeare'sOthello and criticism on it, I had to constantly look up the word "egregious" since the villain uses that word: outstandingly bad or shocking.
Colon before explanation
I guess I can say I had a rough weekend: I had chest pain and spent all Saturday and Sunday in the emergency room.
Some writers use fragments (incomplete sentences) before a colon for emphasis or stylistic preferences (to show a character's voice in literature), as in this example:
Dinner: chips and juice. What a well-rounded diet I have.
The Bedford Handbook describes several uses of a colon. For example, one can use a colon after an independent clause to direct attention to a list, anappositive, or a quotation, and it can be used between independent clauses if the second summarizes or explains the first. In non-literary or non-expository uses, one may use a colon after the salutation in a formal letter, to indicate hours and minutes, to show proportions, between a title and subtitle, and between city and publisher in bibliographic entries.[14]
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, andsegmental.[15]
An appositive colon also separates thesubtitle of a work from its principal title. (In effect, the example given above illustrates an appositive use of the colon as an abbreviation for the conjunction "because".) Dillon has noted the impact of colons on scholarly articles,[20][21] but the reliability of colons as a predictor of quality or impact has also been challenged.[22][23] In titles, neither needs to be a complete sentence as titles do not representexpository writing:
Like adash orquotation mark, a segmental colon introducesspeech. The segmental function was once a common means of indicating an unmarked quotation on the same line. The following example is from the grammar bookThe King's English:
Benjamin Franklin proclaimed the virtue of frugality: A penny saved is a penny earned.
This form is still used in British industry-standard templates for written performancedialogues, such as in aplay.[24] The colon indicates that the words following an character's name are spoken by that character.
Patient: Doctor, I feel like a pair of curtains.
Doctor: Pull yourself together!
The uniform visual pattern of<character_nametag : character_spoken_lines> placement on a script page assists an actor in scanning for the lines of their assigned character during rehearsal, especially if a script is undergoing rewrites between rehearsals.
Use of capitalization or lower-case after a colon varies. InBritish English, and in mostCommonwealth countries, the word following the colon is in lower case unless it is normally capitalized for some other reason, as withproper nouns andacronyms. British English also capitalizes a new sentence introduced by a colon'ssegmental use.[citation needed]
In manyEuropean languages, the colon is usually followed by a lower-case letter unless the upper case is required for other reasons, as with British English.German usage requires capitalization ofindependent clauses following a colon.[26]Dutch further capitalizes the first word of any quotation following a colon, even if it is not a complete sentence on its own.[27]
In print, a thin space was traditionally placed before a colon and a thick space after it. In modernEnglish-language printing, no space is placed before a colon and a single space is placed after it.[28][29] InFrench-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 bymonospaced fonts) was to usetwo spaces after a colon.[30]
In modern typography, a colon will be placed outside the closingparenthesis introducing a list. In very early English typography, it could be placed inside, as seen inRoger Williams' 1643 book about the Native American languages of New England.[31]
Written Swedish uses colons incontractions, such asS:t forSankt (Swedish for "Saint") – for example in the name of theStockholm metro stationS:t Eriksplan, andk:a forkyrka ("church") – for instanceSvenska k:a (Svenska kyrkan), the Evangelical Lutheran national Church of Sweden. This can even occur in people's names, for exampleAntonia Ax:son Johnson (Ax:son forAxelson).Early Modern English texts also used colons to mark abbreviations.[32][33]
InGerman,Hebrew, and sometimes inEnglish, a colon divides the scores of opponents in sports and games. A result of149–0 would be written as 149 : 0 in German and in Hebrew.
When a ratio isreduced to a simpler form, such as 10:15 to 2:3, this may be expressed with adouble colon as 10:15::2:3; this would be read "10 is to 15 as 2 is to 3". This form is also used in tests of logic where the question of "Dog is to Puppy as Cat is to _____?" can be expressed as "Dog:Puppy::Cat:_____". For these uses, there is a dedicatedUnicode symbol (U+2236∶RATIO) that is preferred in some contexts. Compare 2:3 (ratio colon) with 2:3 (U+003A ASCII colon).
(S is the set of allx in (thereal numbers) such thatx is strictly greater than 1 and strictly smaller than 3)
In older literature on mathematical logic, it is used to indicate how expressions should be bracketed (seeGlossary ofPrincipia Mathematica).
Intype theory andprogramming language theory, the colon sign after a term is used to indicate its type, sometimes as a replacement to the "∈" symbol. Example:
.
A colon is also sometimes used to indicate atensor contraction involving two indices, and a double colon (::) for a contraction over four indices.
A colon is also used to denote aparallel sum operation involving two operands (many authors, however, instead use a∥ sign and a few even a∗ for this purpose).
The character was on early typewriters and therefore appeared in most text encodings, such asBaudot code andEBCDIC. It was placed at code 58 inASCII and from there inherited into Unicode. Unicode also defines several related characters:
U+003A:COLON
U+02D0ːMODIFIER LETTER TRIANGULAR COLON, used inIPA.[34]
U+10781𐞁MODIFIER LETTER SUPERSCRIPT TRIANGULAR COLON, IPA modifier-letter.[35]
U+02D1ˑMODIFIER LETTER HALF TRIANGULAR COLON, used in IPA.
U+10782𐞂MODIFIER LETTER SUPERSCRIPT HALF TRIANGULAR COLON, IPA modifier-letter.[35]
U+A789꞉MODIFIER LETTER COLON, seeColon (letter). (This character is also sometimes used inWindowsfilenames as it is identical to the colon in theSegoe UI font used for filenames. The colon itself is not permitted as it is areserved character.)
U+FE13︓PRESENTATION FORM FOR VERTICAL COLON, compatibility character for the Chinese StandardGB 18030.
Many programming languages, most notablyALGOL,Pascal andAda, use a colon and equals sign:= as theassignment operator, to distinguish it from a single equals= which is an equality test (C instead uses a single equals as assignment, and a double equals== as the equality test).[38][39]
Many languages includingC andJava use the colon to indicate the text before it is alabel, such as a target for agoto or an introduction to a case in aswitch statement.[40]: 131 [41] In a related use,Python uses a colon to separate a control statement (theclause header) from the block of statements it controls (thesuite):[42]
iftest(x):print("test(x) is true!")else:print("test(x) is not true...")
The colon is used as part of the?: conditional operator in C and many other languages.[40]: 90
C++ uses a double colon as thescope resolution operator, andclass member access.[45] Most other languages use a period but C++ had to use this for compatibility with C. Another language using colons for scope resolution isErlang, which uses a single colon.[46]
InBASIC, it is used as a separator between the statements or instructions in a single line. Most other languages use a semicolon, but BASIC had used semicolon to separate items in print statements.[47]
InForth, a colonprecedes definition of a new word.[48]
Haskell uses a colon (pronounced as "cons", short for "construct") as an operator to add adata element to the front of alist:[49]
TheML languages (such asStandard ML) 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.[51]: 20, 70
MATLAB uses the colon as a binary operator to generate a vector, or to select a part of an extant matrix.
to introduce acontrol structure element. In this usage it must be the first non-blank character of the line.[52]: 64
after a label name that will be the target of a:goto or a right-pointing arrow (this style of programming is deprecated and programs are supposed to use control structures instead).[52]: 64
to separate a guard (Boolean expression) from its expression in a dynamic function.[52]: 111 Two colons are used for an Error guard (one or more error numbers).[52]: 115
Colon + space are used in class definitions to indicate inheritance.[52]: 135
⍠ (a colon in a box) is used by APL for its variant operator.[52]: 340
The colon is also used in many operating systems commands.[53]
InMicrosoft Windowsfilenames, the colon is reserved for use inalternate data streams and cannot appear in a filename.[57] It was used as the directory separator inClassic Mac OS, and was difficult to use in early versions of the newerBSD-basedmacOS due to code swapping the slash and colon to try to preserve this usage. In most systems it is often difficult to put a colon in a filename as the shell interprets it for other purposes.
CP/M and early versions ofMSDOS required the colon after the names of devices, such asCON: though this gradually disappeared except for disks (where it had to be between the disk name and the requiredpath representation of the file as inC:\Windows\). This then migrated to use inURLs.[55]
It is often used as a single post-fixdelimiter, 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 usedMediaWiki, utilize the colon as both a pre-fix and post-fix delimiter.
Inwiki markup, the colon is often used to indent text. Common usage includes separating or marking comments in a discussion as replies, or to distinguish certain parts of a text.
Markup
Renders as
Normal text.:Indented text by the means of a colon.::The gap increases with colon number.
Normal text.
Indented text by the means of a colon.
The gap increases with colon number.
In human-readable text messages, a colon, or multiple colons, is sometimes used to denote an action (similar to howasterisks are used)[original research?] or to emote (for example, invBulletin). In the action denotation usage 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 asterisks or other punctuation marks.
Colons can also be used to represent eyes inemoticons.
^Trask, Larry (1997)."The Colon". University of Sussex.Archived from the original on 16 January 2018. Retrieved28 November 2014.
^John Mason's work,An Essay on Elocution (1748), notes that "A Comma Stops the Voice while we may privately tell one, a Semi Colon two; a Colon three: and a Period four."
^Serianni, Luca; Castelvecchi, Alberto (1988).Grammatica italiana. Italiano comune e lingua letteraria. Suoni, forme, costrutti (in Italian).Turin: UTET.ISBN88-02-04154-7.
^Peters, Pam (1995). Grayston, Graham (ed.).The Cambridge Australian English style guide. Cambridge: Cambridge University Press. p. 146.ISBN978-0-521-43401-0.
^Dillon, J. T. (1981). "The emergence of the colon: An empirical correlate of scholarship".American Psychologist.36 (8):879–884.doi:10.1037/0003-066x.36.8.879.
^Dillon, J. T. (1982). "In Pursuit of the Colon: A Century of Scholarly Progress: 1880-1980".The Journal of Higher Education.53 (1):93–99.doi:10.2307/1981541.JSTOR1981541.
^Lupo, James; Kopelman, Richard E. (1987). "Punctuation and publishability: A reexamination of the colon".American Psychologist.42 (5): 513.doi:10.1037/0003-066x.42.5.513.a.
^DeRespinis, Francis; Hayward, Peter; Jenkins, Jana; Laird, Amy; McDonald, Leslie; Radzinski, Eric (2012).The IBM Style Guide: Conventions for Writers and Editors. Boston: IBM Press. p. 43.
^Gibaldi, Joseph (2008).MLA Style Manual and Guide to Scholarly Publishing. New York: Modern Language Association of America. p. 91.
^Paterson, Derek (19 November 2009)."How many spaces after a colon?".Absolute Write forums. Post 4.Archived from the original on 27 September 2013. Retrieved4 November 2012.Back in the typewriter day, when fading ink ribbons could result in commas being mistaken for periods and vice versa, typists were taught to insert 2 spaces after the period to differentiate between the two. The same happened with colons and semicolons: 2 spaces were left after a colon; 1 space after a semicolon.
^Compare:Mueller, Janel; Scodel, Joshua, eds. (2009).Elizabeth I: translations, 1544-1589. University of Chicago Press. p. 460.ISBN9780226201337.In the medieval and early modern eras, [...] the colon and raised dot [...] signal a contracted word [...].
^ECMA TC39 (June 2022).ECMA-262(PDF) (13th ed.). Ecma International.Archived(PDF) from the original on 4 July 2022.{{cite book}}: CS1 maint: numeric names: authors list (link)
^"Identifiers".C++ Reference. 16 June 2022. Archived from the original on 22 July 2022. Retrieved28 July 2022.{{cite web}}: CS1 maint: bot: original URL status unknown (link)
^"Core: Glossary".Forth Standard. Forth-Standard-Committee.Archived from the original on 17 November 2015.
^O'Sullivan, Bryan; Stewart, Don; Goerzen, John (2007–2008).Getting Started. Real World Haskell.Archived from the original on 10 July 2012. Retrieved8 November 2011.
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