Colon (punctuation)
[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.
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.
[12] In modern English usage, a complete sentence precedes a colon, while a list, description, explanation, or definition follows it.
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.
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.
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.
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.
[citation needed] American English permits writers to similarly capitalize the first word of any independent clause following a colon.
[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.
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.
In Armenian, a colon indicates the end of a sentence, similar to a Latin full stop or period.
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").
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".
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).
[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.
[51]: 20, 70 MATLAB uses the colon as a binary operator to generate a vector, or to select a part of an extant matrix.
[53] In the esoteric programming language INTERCAL, the colon is called two-spot and used to label a 32-bit variable, distinct from spot (.)
[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.
Common usage includes separating or marking comments in a discussion as replies, or to distinguish certain parts of a text.
