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Colon | |
U+003A:COLON (:) | |
The colon, :, is a punctuation 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 in medical journal citations, [3] between chapter and verse in Bible citations, [4] and, in the US, for salutations in business letters and other formal letters. [1]
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 the 3rd century BC, Aristophanes of Byzantium is alleged to have devised a punctuation system, in which the end of such a kôlon was thought to occasion a medium-length breath, and was marked by a middot · . In practice, evidence is scarce for its early usage, but it was revived later as the ano teleia , the modern Greek semicolon. [6] Some writers also used a double dot symbol ⁚, that later came to be used as a full stop or to mark a change of speaker. (See also Punctuation in Ancient Greek .)
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, [...]
In 1622, in Nicholas Okes' print of William Shakespeare's Othello , the typographical construction of a colon followed by a hyphen or dash to indicate a restful pause is attested. [8] This construction, known as the dog's bollocks , was once common in British English, though this usage is now discouraged. [9] [10] [11]
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]
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]
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:
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]
The colon introduces the logical consequence, or effect, of a fact stated before.
In this sense the colon introduces a description; in particular, it makes explicit the elements of a set.
Syntactical-descriptive colons may separate the numbers indicating hours, minutes, and seconds in abbreviated measures of time. [16]
British English and Australian English, however, more frequently uses a point for this purpose:
A colon is also used in the descriptive location of a book verse if the book is divided into verses, such as in the Bible or the Quran:
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:
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 :
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.
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. 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 ]
American English permits writers to similarly capitalize the first word of any independent clause following a colon. 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 , however, requires capitalization only when the colon introduces a direct quotation, a direct question, or two or more complete sentences. [25] [ failed verification ]
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]
In Finnish and Swedish, the colon can appear inside words in a manner similar to the apostrophe in the English possessive case, connecting a grammatical suffix to an abbreviation or initialism, a special symbol, or a digit (e.g., Finnish USA:n and Swedish USA:s for the genitive case of "USA", Finnish %:ssa for the inessive case of "%", or Finnish 20:een for the illative case of "20").
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]
In Ethiopia, both Amharic and Ge'ez script used and sometimes still use a colon-like mark as word separator.
Historically, a colon-like mark was used as a word separator in Old Turkic script.
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.
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.
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The colon is used in mathematics, cartography, model building, and other fields, in this context it denotes a ratio or a scale, as in 3:1 (pronounced "three to one"). [1]
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).
In some languages (e.g. German, Russian, and French), the colon is the commonly used sign for division (instead of ÷).
The notation |G : H| may also denote the index of a subgroup.
The notation ƒ : X → Y indicates that f 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:
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).
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:
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...")
In many languages, including JavaScript, colons are used to define name–value pairs in a dictionary or object. [43] : 96–100 This is also used by data formats such as JSON. [44] Some other languages use an equals sign.
varobj={name:"Charles",age:18,}
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]
"child":["woman","man"]-- equals ["child","woman","man"]
while a double colon ::
is read as "has type of" (compare scope resolution operator): [50]
("text",False)::([Char],Bool)
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.
APL uses the colon:
:goto
or a right-pointing arrow (this style of programming is deprecated and programs are supposed to use control structures instead). [52] : 64 The colon is also used in many operating systems commands. [53]
In the esoteric programming language INTERCAL, the colon is called two-spot and used to label a 32-bit variable, distinct from spot (.) to label a 16-bit variable. [54] : 3
Internet URLs use the colon to separate the protocol (such as http:
) from the hostname or IP address. [55]
In an IPv6 address, colons (and one optional double colon) separate up to 8 groups of 16 bits in hexadecimal representation. [56] In a URL, a colon follows the initial scheme name (such as Hypertext Transfer Protocol (HTTP) and File Transfer Protocol (FTP), and separates a port number from the hostname or IP address. [55]
In Microsoft Windows filenames, 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.
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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:
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.
Punctuation marks are marks indicating how a piece of written text should be read and, consequently, understood. The oldest known examples of punctuation marks were found in the Mesha Stele from the 9th century BC, consisting of points between the words and horizontal strokes between sections. The alphabet-based writing began with no spaces, no capitalization, no vowels, and with only a few punctuation marks, as it was mostly aimed at recording business transactions. Only with the Greek playwrights did the ends of sentences begin to be marked to help actors know when to make a pause during performances. Punctuation includes space between words and both obsolete and modern signs.
The comma, is a punctuation mark that appears in several variants in different languages. Some typefaces render it as a small line, slightly curved or straight, but inclined from the vertical, others give it the appearance of a miniature filled-in figure 9 placed on the baseline. In many typefaces it is the same shape as an apostrophe or single closing quotation mark ’.
The apostrophe is a punctuation mark, and sometimes a diacritical mark, in languages that use the Latin alphabet and some other alphabets. In English, the apostrophe is used for three basic purposes:
A bracket is either of two tall fore- or back-facing punctuation marks commonly used to isolate a segment of text or data from its surroundings. They come in four main pairs of shapes, as given in the box to the right, which also gives their names, that vary between British and American English. "Brackets", without further qualification, are in British English the (...) marks and in American English the [...] marks.
The hyphen‐ is a punctuation mark used to join words and to separate syllables of a single word. The use of hyphens is called hyphenation.
The question mark? is a punctuation mark that indicates a question or interrogative clause or phrase in many languages.
The semicolon; is a symbol commonly used as orthographic punctuation. In the English language, a semicolon is most commonly used to link two independent clauses that are closely related in thought, such as when restating the preceding idea with a different expression. When a semicolon joins two or more ideas in one sentence, those ideas are then given equal rank. Semicolons can also be used in place of commas to separate items in a list, particularly when the elements of the list themselves have embedded commas.
An interpunct·, also known as an interpoint, middle dot, middot, centered dot or centred dot, is a punctuation mark consisting of a vertically centered dot used for interword separation in Classical Latin. It appears in a variety of uses in some modern languages.
In writing, a space is a blank area that separates words, sentences, syllables and other written or printed glyphs (characters). Conventions for spacing vary among languages, and in some languages the spacing rules are complex. Inter-word spaces ease the reader's task of identifying words, and avoid outright ambiguities such as "now here" vs. "nowhere". They also provide convenient guides for where a human or program may start new lines.
The tilde is a grapheme ⟨˜⟩ or ⟨~⟩ with a number of uses. The name of the character came into English from Spanish tilde, which in turn came from the Latin titulus, meaning 'title' or 'superscription'. Its primary use is as a diacritic (accent) in combination with a base letter. Its freestanding form is used in modern texts mainly to indicate approximation.
The equals sign or equal sign, also known as the equality sign, is the mathematical symbol =, which is used to indicate equality in some well-defined sense. In an equation, it is placed between two expressions that have the same value, or for which one studies the conditions under which they have the same value.
The hyphen-minus symbol - is the form of hyphen most commonly used in digital documents. On most keyboards, it is the only character that resembles a minus sign or a dash so it is also used for these. The name hyphen-minus derives from the original ASCII standard, where it was called hyphen (minus). The character is referred to as a hyphen, a minus sign, or a dash according to the context where it is being used.
This comparison of programming languages compares the features of language syntax (format) for over 50 computer programming languages.
The exclamation mark! is a punctuation mark usually used after an interjection or exclamation to indicate strong feelings or to show emphasis. The exclamation mark often marks the end of a sentence, for example: "Watch out!". Similarly, a bare exclamation mark is often used in warning signs. The exclamation mark is often used in writing to make a character seem as though they are shouting, excited, or surprised.
Japanese punctuation includes various written marks, which differ from those found in European languages, as well as some not used in formal Japanese writing but frequently found in more casual writing, such as exclamation and question marks.
Writing systems that use Chinese characters also include various punctuation marks, derived from both Chinese and Western sources. Historically, jùdòu annotations were often used to indicate the boundaries of sentences and clauses in text. The use of punctuation in written Chinese only became mandatory during the 20th century, due to Western influence. Unlike modern punctuation, judou marks were added by scholars for pedagogical purposes and were not viewed as integral to the text. Texts were therefore generally transmitted without judou. In most cases, this practice did not interfere with the interpretation of a text, although it occasionally resulted in ambiguity.
The dash is a punctuation mark consisting of a long horizontal line. It is similar in appearance to the hyphen but is longer and sometimes higher from the baseline. The most common versions are the en dash–, generally longer than the hyphen but shorter than the minus sign; the em dash—, longer than either the en dash or the minus sign; and the horizontal bar―, whose length varies across typefaces but tends to be between those of the en and em dashes.
The full stop, period, or full point. is a punctuation mark used for several purposes, most often to mark the end of a declarative sentence.
The colon alphabetic letter ꞉ is used in a number of languages and phonetic transcription systems, for vowel length in Americanist Phonetic Notation, for the vowels ⟨a꞉⟩ and ⟨o꞉⟩ in a number of languages of Delhi, India, and for grammatical tone in several languages of Africa. It resembles but differs from the colon punctuation mark, :. In some fonts, the two dots are placed a bit closer together than those of the punctuation colon so that the two characters are visually distinct. In Unicode it has been assigned the code U+A789꞉MODIFIER LETTER COLON, which behaves like a letter rather than a punctuation mark in electronic texts. In practice, however, an ASCII colon is frequently used for the letter.
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.
In the medieval and early modern eras, [...] the colon and raised dot [...] signal a contracted word [...].
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