The slash is an oblique slanting line punctuation mark. Once used to mark periods and commas, the slash is now most often used to represent exclusive or inclusive or, division and fractions, and as a date separator. It is called a solidus in Unicode, it is sometimes known as a stroke in British English, and it has several other historical or technical names, including oblique and virgule.
A slash in the reverse direction (\) is known as a backslash.
Slashes may be found in early writing as a variant form of dashes, vertical strokes, etc. The present use of a slash distinguished from such other marks derives from the medieval European virgule (Latin: virgula, which was used as a period, scratch comma, and caesura mark. (The first sense was eventually lost to the low dot and the other two developed separately into the comma ⟨,⟩ and caesura mark ⟨||⟩.) Its use as a comma became especially widespread in France, where it was also used to mark the continuation of a word onto the next line of a page, a sense later taken on by the hyphen ⟨-⟩. The Fraktur script used throughout Central Europe in the early modern period used a single slash as a scratch comma and a double slash (//) as a dash. The double slash developed into the double oblique hyphen ⟨?⟩ and double hyphen ⟨=⟩ or ⟨=⟩ before being usually simplified into various single dashes.
In the 18th century, the mark was generally known in English as the "oblique". The variant "oblique stroke" was increasingly shortened to "stroke", which became the common British name for the character, although printers and publishing professionals often instead referred to it as an "oblique". In the 19th and early 20th century, it was also widely known as the "shilling mark" or "solidus", from its use as the currency sign for the shilling. The name "slash" is a recent development, first attested in American English c. 1961, but has gained wide currency through its use in computing, a context where it is sometimes even used in British English in preference to the usual name "stroke". Clarifying terms such as "forward slash" have been coined owing to widespread use of Microsoft's DOS and Windows operating systems, which use the backslash extensively.
The slash is commonly used in many languages as a shorter substitute for the conjunction "or", typically with the sense of exclusive or (e.g., Y/N permits yes or no but not both). Its use in this sense is somewhat informal, although it is used in philology to note variants (e.g., virgula/uirgula) and etymologies (e.g., 
Such slashes may be used to avoid taking a position in naming disputes. One example is the Syriac naming dispute, which prompted the US and Swedish censuses to use the respective official designations "Assyrian/Chaldean/Syriac" and "Assyrier/Syrianer" for the ethnic group.
In particular, since the late 20th century, the slash is used to permit more gender-neutral language in place of the traditional masculine or plural gender neutrals. In the case of English, this is usually restricted to degendered pronouns such as "he/she" or "s/he". Most other Indo-European languages include more far-reaching use of grammatical gender. In these, the separate gendered desinences (grammatical suffices) of the words may be given divided by slashes or set off with parentheses. For example, in Spanish, hijo is a son and a hija is a daughter; some proponents of gender-neutral language advocate the use of hijo/a or hijo(a) when writing for a general audience or addressing a listener of unknown gender. Less commonly, the æligature or at sign ⟨@⟩ is used instead: hij@. Similarly, in German, Sekretär refers to any secretary and Sekretärin to an explicitly female secretary; some advocates of gender neutrality support forms such as Sekretär/-in for general use. This does not always work smoothly, however: problems arise in the case of words like Arzt ("doctor") where the explicitly female form Ärztin is umlauted and words like Chinese ("Chinese person") where the explicitly female form Chinesin loses the terminal -e.
The slash is also used as a shorter substitute for the conjunction "and" or inclusive or (i.e., A or B or both), typically in situations where it fills the role of a hyphen or en dash. For example, the "Hemingway/Faulkner generation" might be used to discuss the era of the Lost Generation inclusive of the people around and affected by both Hemingway and Faulkner. This use is sometimes proscribed, as by New Hart's Rules, the style guide for the Oxford University Press.
The word "slash" is also developing as a way to introduce topic shifts or follow-up statements. "Slash" can introduce a follow up statement, such as, "I really love that hot dog place on Liberty Street. Slash can we go there tomorrow?" It can also indicate a shift to an unrelated topic, as in "JUST SAW ALEX! Slash I just chubbed on oatmeal raisin cookies at north quad and i miss you." The new usage of "slash" appears most frequently in spoken conversation, though it can also appear in writing.
The fraction slash ⟨ / ⟩, is used between two numbers to indicate a fraction or ratio. Fractions, unlike inline division, are often given using smaller numbers, superscript, and subscript (e.g., ²³/). Such formatting developed as a way to write the horizontal fraction bar on a single line of text. It is first attested in England and Mexico in the 18th century. This notation is known as an online, solidus, or shilling fraction. This notation is responsible for the current form of the percent ⟨%⟩, permille ⟨?⟩, and permyriad ⟨?⟩ signs, developed from the horizontal form which represented an early modern corruption of an Italian abbreviation of per cento.
The separate encoding of the Unicode fraction slash is intended to permit automatic formatting of the preceding and succeeding digits by glyph substitution with numerator and denominator glyphs (e.g., display of 11/12 as ), although this may not yet be supported in certain environments and fonts. By lack of support, some authors still use Unicode subscripts and superscripts to compose fractions, the more as in many popular fonts, these characters are repurposed as numerators and denominators. A number of common fractions--with their slashes--are specially encoded in Unicode, including ½, 1/3 , ¼, and 1/8 .
The division slash ⟨/⟩, is used between two numbers to indicate division (e.g., 23÷43 can also be written as 23/43). This use developed from the fraction slash in the late 18th or early 19th century. The formatting was advocated by De Morgan in the mid-19th century.
A quotient of a set is informally a new set obtained by identifying some elements of the original set. This is denoted as a fraction (sometimes even as a built fraction), where the numerator is the original set (often equipped with some algebraic structure). What is appropriate as denominator depends on the context.
In the most general case, the denominator is an equivalence relation on the original set , and elements are to be identified in the quotient if they are equivalent according to ; this is technically achieved by making the set of all equivalence classes of .
In group theory, the slash is used to mark quotient groups. The general form is , where is the original group and is the normal subgroup; this is read " mod ", where "mod" is short for "modulo". Formally this is a special case of quotient by an equivalence relation, where iff for some . Since many algebraic structures (rings, vector spaces, etc.) in particular are groups, the same style of quotients extend also to these, although the denominator may need to satisfy additional closure properties for the quotient to preserve the full algebraic structure of the original (e.g. for the quotient of a ring to be a ring, the denominator must be an ideal).
When the original set is the set of integers , the denominator may alternatively be just an integer: . This is an alternative notation for the set of integers modulo n (needed because is also notation for the very different ring of n-adic integers). is an abbreviation of or , which both are ways of writing the set in question as a quotient of groups.
Slashes may also be used as a combining character in mathematical formulae. The most important use of this is that combining a slash with a relation negates it, producing e.g. 'not equal' as negation of or 'not in' as negation of ; these slashed relation symbols are always implicitly defined in terms of the non-slashed base symbol. The graphical form of the negation slash is mostly the same as for a division slash, except in some cases where that would look odd; the negation of (divides) and negation of (various meanings) customarily both have their negations slashes less steep and in particular shorter than the usual one.
The Feynman slash notation is an unrelated use of combining slashes, mostly seen in quantum field theory. This kind of combining slash takes a vector base symbol and converts it to a matrix quantity. Technically this notation is a shorthand for contracting the vector with the Dirac gamma matrices, so ; what one gains is not only a more compact formula, but also not having to allocate a letter as the contracted index.
The slash is used as the path component separator in many computer operating systems (e.g., Unix's pictures/image.png). In Unix and Unix-like systems, such as macOS and Linux, the slash is also used for the volume root directory (e.g., the initial slash in /usr/john/pictures). Confusion of the slash with the backslash ⟨\⟩ largely arises from the use of the latter as the path component separator in the widely used MS-DOS, Windows, and OS/2 systems.
The slash is used in a similar fashion in internet URLs (e.g., http://www.popflock.com/learn?s=Slash_(punctuation)). Often a portion of such URLs corresponds with files on a Unix server with the same name.
The slash in an IP address (e.g., 192.0.2.0/29) indicates the prefix size in CIDR notation. The number of addresses of a subnet may be calculated as 2address size - prefix size, in which the address size is 128 for IPv6 and 32 for IPv4. For example, in IPv4, the prefix size /29 gives: 232-29 = 23 = 8 addresses.
The slash is used as a division operator in most programming languages while APL uses it for reduction (fold) and compression (filter). The double slash is used by Rexx as a modulo operator, and Python (starting in version 2.2) uses a double slash for division which rounds (using floor) to an integer. In Perl 6 the double slash is used as a "defined-or" alternative to ||. A dot and slash ⟨./⟩ is used in MATLAB and GNU Octave to indicate an element-by-element division of matrices.
In SGML and derived languages such as HTML and XML, a slash is used in closing tags. For example, in HTML, <b> begins a section of bold text and </b> closes it. In XHTML, slashes are also necessary for "self-closing" elements such as the newline command where HTML has simply .
Windows, DOS, some CP/M programs, OpenVMS, and OS/2 all use the slash to indicate command-line options. For example, the command dir/w is understood as using the command dir ("directory") with the "wide" option. Notice that no space is required between the command and the switch; this was responsible for the choice to use backslashes as the path separator since one would otherwise be unable to run a program in a different directory.
Slashes are used as the standard delimiters for regular expressions, although other characters can be used instead.
IBM JCL uses a double slash to start each line in a batch job stream except for /* and /&.
IRC and many in-game chat clients use the slash to mark commands, such as joining and leaving a chat room or sending private messages. For example, in IRC, /join #services is an command to join the channel "services" and /me is a command to format the following message as though it were an action instead of a spoken message. In Minecrafts chat function, the slash is used for executing console and plugin commands. In Second Lifes chat function, the slash is used to select the "communications channel", allowing users to direct commands to virtual objects "listening" on different channels. For example, if a virtual house's lights were set to use channel 42, the command "/42 on" would turn them on.
The slash (as the "shilling mark" or "solidus") was the currency sign of the shilling, a former coin of the United Kingdom and its former colonies. Before the decimalization of currency in Britain, its currency symbols (collectively £sd) represented their Latin names, derived from a medieval French modification of the late Roman libra, solidus, and denarius. Thus, one penny less than two pounds was written During the period when English orthography included the long s ⟨s⟩, the s. (that is, s.) came to be written as a single slash. When the d. fell out of general use, one penny less than two pounds was written Similarly, "2/6" meant two shillings sixpence. In Britain, exactly five shillings was typically written "5/-" while, in East Africa, it was more common to mark it with a double hyphen as "5/=". The same style was also used under the British Raj and early independent India for the predecimalization rupee/anna/pie system.
In decimalized currency, a slash followed by a dash ⟨/-⟩ continues to be used in some places to mark an exact amount of currency with no subunits. For example, "£50/-" is a variant of £50.00 and serves a similar function of providing clarity and ensuring that no further digits are added to the end of the number.
The slash is used in currency exchange rate notation to express exchange rates, the ratio of the first currency in terms of the second. For example, EUR/USD x expresses that the value of 1 euro in terms of US dollars is x. This value may then be multiplied by any number of euros to find its value in dollars.
Slashes are a common calendar date separator used across many countries and by some standards such as the Common Log Format used by web servers. Depending on context, it may be in the form Day/Month/Year, Month/Day/Year, or Year/Month/Day. If only two elements are present, they typically denote a day and month in some order. For example, 9/11 is a common American way of writing the date September 11 and has become shorthand for the attacks on New York and Washington, DC, which occurred on a day Britons write as 11/9/2001. Owing to the ambiguity across cultures, the practice of using only two elements to denote a date is sometimes proscribed.
Because of the world's many varying conventional date and time formats, ISO 8601 advocates the use of a Year-Month-Day system separated by hyphens (e.g., Armistice Day first occurred on 1918-11-11). In the ISO 8601 system, slashes represent date ranges: "1939/1945" represents what is more commonly written with an en dash as "1935-1945" or with a hyphen as "1935-1945". The autumn term of a northern-hemisphere school year might be marked "2010-09-01/12-22". This formal notation is sometimes[when?] emended to use double hyphens instead (as 1939--1945) to permit its use in file names.
In English, a range marked by a slash often has a separate meaning from one marked by a dash or hyphen. "24/25 December" would mark the time shared by both days (i.e., the night from Christmas Eve to Christmas morning) rather than the time made up by both days together, which would be written "24-25 December". Similarly, a historical reference to "1066/67" might imply an event occurred during the winter of late 1066 and early 1067, whereas a reference to 1066-67 would cover the entirety of both years. The usage was particularly common in British English during World War II, where such slash dates were used for night-bombing air raids. It is also used by some police forces in the United States.
The slash is used in numbering to note totals. For example, "page 17/35" indicates that the relevant passage is on the 17th page of a 35-page document. Similarly, the marking "#333/500" on a product indicates it is the 333rd out of 500 identical products or out of a batch of 500 such products. For scores on schoolwork, in games, &c., "85/100" indicates 85 points were attained out of a possible 100.
Slashes are also sometimes used to mark ranges in numbers that already include hyphens or dashes. One example is the ISO treatment of dating. Another is the US Air Force's treatment of aircraft serial numbers, which are normally written to note the fiscal year and aircraft number. For example, "85-1000" notes the thousandth aircraft ordered in fiscal year 1985. To indicate the next fifty subsequent aircraft, a slash is used in place of a hyphen or dash: "85-1001/1050".
A pair of slashes (as "slants") are used in the transcription of speech to enclose pronunciations (i.e., phonetic transcriptions). For example, the IPA transcription of the English pronunciation of "solidus" is written /'s?l?d?s/. Properly, slashes mark broad or phonemic transcriptions, whereas narrow, allophonic transcriptions are enclosed by square brackets. For example, the word "little" may be broadly rendered as /'l?t?l/ but a careful transcription of the velarization of the second L would be written ['l?].
In sociolinguistics, a double or triple slash may also be used in the transcription of a traditional sociolinguistic interview or in other type of linguistic elicitation to represent simultaneous speech, interruptions, and certain types of speech disfluencies.
The slash (as a "virgule") offset by spaces to either side is used to mark line breaks when transcribing text from a multi-line format into a single-line one. It is particularly common in quoting poetry, song lyrics, and dramatic scripts, formats where omitting the line breaks risks losing meaningful context. For example, when quoting Hamlet's soliloquy
To be, or not to be, that is the question:
Whether 'tis Nobler in the mind to suffer
The Slings and Arrows of outrageous Fortune,
Or to take Arms against a Sea of troubles,
And by opposing end them...
into a prose paragraph, it is standard to mark the line breaks as "To be, or not to be, that is the Whether 'tis nobler in the mind to The slings and arrows of outrageous Or to take arms against a sea of And by opposing end them..." Less often, virgules are used in marking paragraph breaks when quoting a prose passage. Some style guides, such as Hart's, prefer to use a pipe ⟨|⟩ in place of the slash to mark these line and paragraph breaks.
The virgule may be thinner than a standard slash when typeset. In computing contexts, it may be necessary to use a non-breaking space before the virgule to prevent it from being widowed on the next line.
The slash has become standard in several abbreviations. Generally, it is used to mark two-letter initialisms such as A/C (short for "air conditioner"), w/o ("without"), b/w ("black and white" or, less often, "between"), w/e ("whatever" or, less often, "weekend" or "week ending"), i/o ("input/output"), r/w ("read/write"), and n/a ("not applicable"). Other initialisms employing the slash include w/ ("with") and w/r/t ("with regard to"). Such slashed abbreviations are somewhat more common in British English and were more common around the Second World War (as with "S/E" to mean "single-engined"). The abbreviation 24/7 (denoting 24 hours a day, 7 days a week) describes a business that is always open or unceasing activity.
The slash in derived units such as m/s (meters per second) is not an abbreviation slash, but a straight division. It is however in that position read as 'per' rather than e.g. 'over', which can be seen as analogous to units whose symbols are pure abbreviations such as mph (miles per hour), although in abbreviations 'per' is 'p' or dropped entirely (psi, pounds per square inch) rather than a slash.
In the US government, the names of offices within various departments are abbreviated using slashes, starting with the larger office and following with its subdivisions. For example, the Federal Aviation Administration's Office of Commercial Space Transportation is formally abbreviated FAA/AST.
The slash or vertical bar (as a "separatrix") is used in proofreading to mark the end of margin notes[n 1] or to separate margin notes from one another. The slash is also sometimes used in various proofreading initialisms, such as l/c and u/c for changes to lower and upper case, respectively.
The slash is used in fan fiction to mark the romantic pairing a piece will focus upon (e.g., a K/S denoted a Star Trek story would focus on a sexual relationship between Kirk and Spock), a usage which developed in the 1970s from the earlier friendship pairings marked by ampersands (e.g., K&S). The genre as a whole is now known as slash fiction. Because it is more generally associated with homosexual male relationships, lesbian slash fiction is sometimes distinguished as femslash. In situations where other pairings occur, the genres may be distinguished as m/m, f/f, &c.
The slash is used under the Anglo-American Cataloguing Rules to separate the title of a work from its statement of responsibility (i.e., the listing of its author, director, &c.). Like a line break, this slash is surrounded by a single space on either side. For example:
The format is used in both card catalogs and online records.
The slash is sometimes used as an abbreviation for building numbers. For example, in some contexts,[where?] 8/A Evergreen Gardens specifies Apartment 8 in Building A of the residential complex Evergreen Gardens. In the United States, however, such an address refers to the first division of Apartment 8 and is simply a variant of Apartment 8A or 8-A. Similarly in the United Kingdom, an address such as 12/2 Anywhere Road means flat (or apartment) 2 in the building numbered 12 on Anywhere Road.
The slash is used in various scansion notations for representing the metrical pattern of a line of verse, typically to indicate a stressed syllable.
Slashes are used in musical notation as an alternative to writing out specific notes where it is easier to read than traditional notation or where the player can improvise. They are commonly used to indicate chords either in place of or in combination with traditional notation and for drummers as an indication to continue with the previously indicated style.
In online messaging, a slash might be used to imitate the formatting of a chat command (e.g., writing "/fliptable" as though there were such a command) or the closing tags of languages such as HTML (e.g., writing "/endrant" to end an ironic diatribe or "/s" to mark the preceding text as sarcastic). A pair of slashes is sometimes used as a way to mark italic text, where no special formatting is available (e.g., /italics/). A single slash is sometimes used as a way of expressing a check mark, with the meaning "OK", "got it", "done", or "thanks". In Japan, a set of multiple slashes (typically three: ///) is used to convey shyness or embarrassment, owing to the way blushing is depicted in manga. These slashes are usually placed at the end of a statement.
A slash is usually written without spacing on either side when it connects single words, letters, or symbols. It is, however, common to include a space on each side of the slash when it connects items which themselves have spaces--for example, when marking line breaks in quoted verse or when connecting other items with several words such as "our New Western Australia trip". When typesetting a URL or computer path, line breaks should occur before a slash but not in the text between two slashes.
As a very common character, the slash (as slant) was originally encoded in ASCII with the decimal code 47 (0x2F). It is represented in Unicode (as solidus) by the code point with the same value, U+002F.
|diagonal||An uncommon name for the slash in all its uses, but particularly the less vertical fraction slash.|
|division slash||Unicode's formal name for the variant of the slash used to mark division.|
|forward slash||A retronym used to distinguish slash from a backslash following the popularization of MS-DOS and other Microsoft operating systems, which use the backslash for paths in its file system. Less often forward stroke (UK), foreslash, front slash, and frontslash. It is not unknown to even see such back-formations as reverse backslash.|
|fraction slash||Unicode's formal name for the low slash used to marking fractions. Also sometimes known as the fraction bar, although this more properly refers to the horizontal bar.|
|oblique||A formerly common name for the slash in all its uses. Also oblique stroke,oblique dash, &c.|
|A modern name for the virgule's historic use as a form of comma.|
|separatrix||Originally, the vertical line separating integers from decimals before the advent of the decimal point; later used for the vertical bar or slash used in proofreader's marginalia to denote the intended replacement for a letter or word struckthrough in proofed text or to separate margin notes. Sometimes misapplied to virgules.|
|shilling mark||A development of the long S ⟨s⟩ used as a currency symbol for the former English shilling (Latin: solidus). Also known as a shilling stroke. Now obsolete except in historical contexts.|
|slant||From its shape, an infrequent name except (as slants) in its use to mark pronunciations off from other text and as the official ASCII name of the character. Also slant line(s) or bar(s).|
|slash mark||An alternative name used to distinguish the punctuation mark from the word's other senses.|
|slat||An uncommon name for the slash used by the esoteric programming language INTERCAL. Also slak.|
|solidus||Another name for the shilling mark (from the Latin form of its name), also applied to other slashes separating numbers or letters, adopted by the ISO and Unicode as their formal name for the slash. When used as a fraction bar, the solidus is less vertical than a standard slash, generally close to 45° and kerned on both sides; this use is distinguished by Unicode as the fraction slash. (This use is sometimes mistakenly described as the sole meaning of "solidus", with its use as a shilling mark and slash distinguished under the name "virgule".) The solidus's use as a division sign is distinguished as the division slash. The "combining short" or "long solidus overlay" is a diagonal strikethrough.|
|stroke||A common British name for the slash in nearly all its uses, a contraction of oblique stroke popularized by its use in telegraphy. It is particularly employed in reading the mark out loud: "he stroke she" is the common British reading of "he/she". "Slash" has, however, become common in Britain in computing contexts, while some North American amateur radio enthusiasts employ the British "stroke". Less frequently, "stroke" is also used to refer to hyphens.|
|virgule||A development of virgula ("twig"), the original medieval Latin name of the character when it was used as a period, scratch comma, and caesura mark. Now primarily used as the name of the slash when it is used to mark line breaks in quotations. Sometimes mistakenly distinguished as a formal name for the slash, as against the solidus's supposed use as a fraction slash. Formerly sometimes anglicized in British sources as the virgil.|
The slash may also be read out as and, or, and/or, to, or cum in some compounds separated by a slash; over or out of in fractions, division, and numbering; and per or a(n) in derived units (as km/h) and prices (as $~/kg), where the division slash stands for "each".