Product Code Database
The colon, , is a punctuation mark consisting of two equally sized dots aligned vertically. A colon often precedes an explanation, a list, or a quoted sentence. It is also used between hours and minutes in time, between certain elements in medical journal citations, between chapter and verse in , between two numbers in a ratio, and, in the US, for in business letters and other formal letters.
In the 3rd century BC, Aristophanes of Byzantium is alleged to have devised a punctuation system, in which the end of such a was thought to occasion a medium-length breath, and was marked by a interpunct . In practice, evidence is scarce for its early usage, but it was revived later as the ano teleia, the modern Greek semicolon. 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 language term colon and the corresponding punctuation mark is attested:
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. This construction, known as the dog's bollocks, was once common in British English, though this usage is now discouraged.
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.
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.
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. (1988). 9788802041544, UTET. ISBN 9788802041544
Syntactical-descriptive colons may separate the numbers indicating , , and in abbreviated measures of time.
British English and Australian English, however, more frequently use a decimal mark 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, but the reliability of colons as a predictor of quality or impact has also been challenged. In titles, neither needs to be a complete sentence as titles do not represent writing:
This form is still used in British industry-standard templates for written performance , such as in a play. The colon indicates that the words following an character's name are spoken by that character.
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.
In many languages, the colon is usually followed by a lowercase letter unless the upper case is required for other reasons, as with British English. German language usage requires capitalization of independent clauses following a colon. Duden Newsletter vom 24 August 2001 Dutch language further capitalizes the first word of any quotation following a colon, even if it is not a complete sentence on its own.
One or two spaces may be and have been used after a colon. The older convention (designed to be used by ) was to use two spaces after a colon.
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.
Historically, a colon-like mark was used as a word separator in Old Turkic script.
In liturgical Hebrew, the sof passuk is used in some writings such as prayer books to signal the end of a verse.
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 () that is preferred in some contexts. Compare (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 may also denote the index of a subgroup.
The notation indicates that is a function with domain and codomain .
The combination with an equal sign () is used for .
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).
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. 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).
In many languages, including JavaScript, colons are used to define name–value pairs in a JSON or object. This is also used by data formats such as JSON. Some other languages use an equals sign.
The colon is used as part of the conditional operator in C and many other languages.
C++ and Rust use a double colon as the scope resolution operator/namespace qualification, and class member access. This is unlike some other languages, which use periods to do so. Another language using colons for scope resolution is Erlang, which uses a single colon. In C#, the double colon is used to access a member of an aliased namespace. Similarly in Java, the double colon is used to retrieve a method reference.
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.
In Forth, a colon precedes definition of a new word.
Haskell uses a colon (pronounced as "cons", short for "construct") as an operator to add a data element to the front of a list, while a double colon :: is read as "has type of" (compare scope resolution operator). 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. Rust, ActionScript, Kotlin, and TypeScript also use a colon to include a type annotation on a function or a variable.
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:
The colon is also used in many operating systems commands.
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.
In an IPv6 address, colons (and one optional double colon) separate up to 8 groups of 16 in hexadecimal representation. 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.
In Microsoft Windows , the colon is reserved for use in alternate data streams and cannot appear in a filename. 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 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.
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.
|
|
