This article is about the punctuation mark. For a colon-like character used as an alphabetic letter in some languages, rather than as punctuation, see Colon (letter). For other uses, see Colon (disambiguation).
In Ancient Greek, in rhetoric and prosody, the term κῶλον (kôlon, lit. 'limb, member of a body') did not refer to punctuation, but to a member or section of a complete thought or passage; see also Colon (rhetoric). From this usage, in palaeography, a colon is a clause or group of clauses written as a line in a manuscript.[5]
In 1589, in The Arte of English Poesie, the English term colon 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 called comma [...] The second they called colon, 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 called periodus, [...]
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, but silent reading eventually replaced this with other considerations.[12]
Usage in English
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's Othello 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, an appositive, 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, and segmental.[15]
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: Daphne, Rose, and Suzanne.
Syntactical-descriptive colons may separate the numbers indicating hours, minutes, and seconds in abbreviated measures of time.[16]
An appositive colon also separates the subtitle 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 represent expository writing:
Star Wars Episode VI: Return of the Jedi
Segmental
Like a dash or quotation mark, a segmental colon 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 British industry-standard templates for written performance dialogues, such as in a play.[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 capitals
Use of capitalization or lower-case after a colon varies. In British English, and in most Commonwealth countries, the word following the colon is in lower case unless it is normally capitalized for some other reason, as with proper nouns and acronyms. British English also capitalizes a new sentence introduced by a colon's segmental use.[citation needed]
In many European 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 of independent 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 modern English-language printing, no space is placed before a colon and a single space is placed after it.[28][29] 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.[30]
In modern typography, a colon will be placed outside the closing parenthesis introducing a list. In very early English typography, it could be placed inside, as seen in Roger Williams' 1643 book about the Native American languages of New England.[31]
Written Swedish uses colons in contractions, such as S:t for Sankt (Swedish for "Saint") – for example in the name of the Stockholm metro station S:t Eriksplan, and k:a for kyrka ("church") – for instance Svenska k:a (Svenska kyrkan), the Evangelical Lutheran national Church of Sweden. This can even occur in people's names, for example Antonia Ax:son Johnson (Ax:son for Axelson). Early Modern English texts also used colons to mark abbreviations.[32][33]
Historically, a colon-like mark was used as a word separator in Old Turkic script.
End of sentence or verse
In Armenian, a colon indicates the end of a sentence, similar to a Latin full stop or period.
In liturgical Hebrew, the sof pasuq is used in some writings such as prayer books to signal the end of a verse.
Score divider
In German, Hebrew, and sometimes in English, a colon divides the scores of opponents in sports and games. A result of 149–0 would be written as 149 : 0 in German and in Hebrew.
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". 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 dedicated Unicode 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 all x in (the real numbers) such that x 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 (see Glossary of Principia Mathematica).
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 "∈" symbol. Example:
.
A colon is also sometimes used to indicate a tensor contraction involving two indices, and a double colon (::) for a contraction over four indices.
A colon is also used to denote a parallel sum operation involving two operands (many authors, however, instead use a ∥ sign and a few even a ∗ for this purpose).
Computing
The character was on early typewriters and therefore appeared in most text encodings, such as Baudot code and EBCDIC. It was placed at code 58 in ASCII and from there inherited into Unicode. Unicode also defines several related characters:
U+003A:COLON
U+02D0ːMODIFIER LETTER TRIANGULAR COLON, used in IPA.[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]
Many programming languages, most notably ALGOL, Pascal and Ada, use a colon and equals sign := as the assignment 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 including C and Java use the colon to indicate the text before it is a label, such as a target for a goto or an introduction to a case in a switch statement.[40]: 131 [41] In a related use, Python uses a colon to separate a control statement (the clause header) from the block of statements it controls (the suite):[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 the scope resolution operator, and class 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 is Erlang, which uses a single colon.[46]
In BASIC, 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]
In Forth, a colon precedes definition of a new word.[48]
Haskell uses a colon (pronounced as "cons", short for "construct") as an operator to add a data element to the front of a list:[49]
The ML languages (such as Standard 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 a control 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]
In Microsoft Windowsfilenames, the colon is reserved for use in alternate data streams and cannot appear in a filename.[57] It was used as the directory separator in Classic Mac OS, and was difficult to use in early versions of the newer BSD-based macOS 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 of MSDOS required the colon after the names of devices, such as CON: though this gradually disappeared except for disks (where it had to be between the disk name and the required path representation of the file as in C:\Windows\). This then migrated to use in URLs.[55]
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.
In wiki 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 how asterisks are used)[original research?] or to emote (for example, in vBulletin). 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 in emoticons.
^Trask, Larry (1997). "The Colon". University of Sussex. Archived from the original on 16 January 2018. Retrieved 28 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. Retrieved 4 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. Retrieved 28 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. Retrieved 8 November 2011.