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The slash (/) is a sign used as a punctuation mark and for various other purposes. It often is called a forward slash (a retronym used to distinguish the slash from the backslash, "\") and many other other names, and sometimes is erroneously called a backslash.
The slash goes back to the days of ancient Rome. In the early modern period, in the Fraktur script, which was widespread through Europe in the Middle Ages, one slash (/) represented a comma, while two slashes (//) represented a dash. The two slashes eventually evolved into a sign similar to the equals sign (=), then being further simplified to a single dash (–) or hyphen (‐).
In English text 
The slash is most commonly used as the word substitute for "or" which indicates a choice (often mutually-exclusive) is present. (Examples: Male/Female, Y/N, He/She. See also the Gender-neutrality in Spanish and Portuguese section below.) The slash is also used to avoid taking a position in a naming controversy, allowing the juxtaposition of both names without stating a preference. An example is the designation "Assyrian/Chaldean/Syriac" in the official U.S. census, reflecting the Syriac naming dispute. The Swedish census has come to a similar solution, using "Assyrier/Syrianer" to refer to the same ethnic group.
The slash is also used to indicate a line break when quoting multiple lines from a poem, play, or headline; or in an ordinary prose quotation, the start of a new paragraph. In this case, a space is placed before and after the slash. For example: "Love alters not with his brief hours and weeks / But bears it out even to the edge of doom". When used this way, the mark is called a virgule. It is thinner than a solidus if typeset.
There are usually no spaces either before or after a slash: "male/female". Exceptions are in representing the start of a new line when quoting verse, or a new paragraph when quoting prose. The Chicago Manual of Style (at 6.104) also allows spaces when either of the separated items is a compound that itself includes a space: "Our New Zealand / Western Australia trip". (Compare use of an en dash used to separate such compounds.) The Canadian Style: A Guide to Writing and Editing prescribes "No space before or after an oblique when used between individual words, letters or symbols; one space before and after the oblique when used between longer groups which contain internal spacing", giving the examples "n/a" and "Language and Society / Langue et société".
The slash is often used, perhaps incorrectly, to separate the letters in a two-letter initialism such as R/C (short for "radio control") or w/o ("without"). Purists[who?] strongly discourage this newer use of the symbol. However, since other uses of the slash with individual characters are highly context-specific, confusion is not likely to arise. Other examples include b/w ("between" or, sometimes, "black and white"), w/e ("whatever", also "weekend" or "week ending"), i/o ("input/output"), r/w ("read/write") and even a one-letter initialism w/ ("with"). British English in particular makes use of the slash instead of the hyphen in forming abbreviations. Many examples are found in writings during the Second World War. For example, "S/E" means "single-engined", as a quick way of writing a type of aircraft.
In the U.S. government, office names are abbreviated using slashes, starting with the larger office and following with its subdivisions. In the State Department, the Office of Commercial & Business Affairs in the Bureau for Economic, Energy and Business Affairs is referred to as EEB/CBA.
When highlighting corrections on a proof, a proofreader will write what he or she thinks should be changed—or why it should be changed—in the margin. They separate the comments with a slash called a separatrix.
When marking an uppercase letter for conversion to lowercase, a proofreader will put a slash through it and write lc or l/c in the margin.
Used between numbers slash means division, and in this sense the symbol may be read aloud as "over". For sets, it usually means modulo (quotient group). Proper typography requires a more horizontal line and the numbers rendered using superscript and subscript, e.g. “123⁄456”.
The solidus // or a shilling mark is a punctuation mark used to indicate fractions including fractional currency. The solidus is significantly more horizontal than the slash. These are two distinct symbols that traditionally have entirely different uses. However, many people no longer distinguish between them, and when there is no alternative it is acceptable to use the slash in place of the solidus. In the UK and British Commonwealth, prior to decimalisation, a solidus symbol was used for shillings; thus "5∕6" meant "five shillings and six pence", and "5∕-" meant "five shillings". Currency sums in pounds, shillings, and pence were abbreviated using the '£' symbol, the 's.' symbol, and the 'd.' symbol (collectively £sd) referring to the libra, the solidus, and the denarius. The 's.' was at one stage written using a long s, ſ, that was further abbreviated to the ∕ symbol, and suppression of the 'd.'; thus '2 pounds, 10 shillings, and 6 pence', often written as £2-10-6 (as an alternative to '£2 10s. 6d.'), and '10 shillings' would often be written as 10∕-. This usage caused the names solidus (given the abbreviation's historical root) and shilling mark to be used as names for this character.
A slash followed by a dash is used at the conclusion of currency if cents are not included. For example, on a check/cheque or a hand-written invoice, somebody may write $50/- (equivalent to $50.00) to denote the end of the currency. This keeps anybody from adding further digits to the end of the number.
CURRENCY EXCHANGE RATE NOTATIONS
Currency exchange rate notations use the forward slash counter-intuitively. For example, the exchange rate for the Euro in U.S. Dollars is noted as "EUR/USD", which many would reasonably read to mean "Euros per Dollar". In practice, it is exactly the opposite: It means U.S. Dollars per Euro. In currency exchange notation, the currency preceding the slash is the Base currency and is always the number "1". The currency after the slash is the "counter-currency" or the "quoted currency". So "EUR/USD" means that One Euro equals "x" number of U.S. Dollars.
In contradiction to the precedent of long-established typesetting terminology, ISO and The Unicode Consortium both designate this character (the common slash or virgule) as U+002F / solidus,(see Currency). Despite amendments to the character metadata (by including aliases, such as "solidus (in typography)" for FRACTION SLASH), this contradiction is likely to persist, as The Unicode Consortium clearly states: "[…] once a character is encoded, its name will not be changed."
Usually the character considered a true solidus is U+2044 ⁄ fraction slash. Unicode standards also intend this character to specifically indicate a fraction, and to flag the rendering engine to realize the numbers as vulgar fractions if possible; for example, so that "1⁄2" can be rendered similar to the single character "½". In addition there is U+2215 ∕ division slash which does not have this typographical effect. Since few fonts and text layout systems have the proper mappings to implement this, FRACTION SLASH is often realized identical to DIVISION SLASH.
The fraction slash is found in the mac-roman character set used on legacy Apple Macintosh computers. It can be typed on a Macintosh computer (with US keyboard layout) by pressing ⌥ Option+⇧ Shift+1 (this produces the Unicode FRACTION SLASH on Mac OS X). The fraction slash can be typed on Microsoft Windows as Alt+8260 and the division slash as Alt+8725.
A leading slash represents the root directory of the virtual file system. It is used when specifying absolute paths:
The slash is sometimes called a "forward slash" to contrast with the backslash, "\", which is also used for the same purpose in DOS, Windows and OS/2 systems. Due to DOS and Windows users often seeing far more backslashes than normal ones, they sometimes incorrectly assume a backslash is normal and incorrectly call a slash a "backslash", or felt they needed to say "forward slash" to ensure the correct one was understood. With the increased visibility of slash in Internet URLs, and increased use of Unix systems (such as Mac OS X and Linux), slashes have again become more common for most computer users.
Slashes are used in URLs in a way similar to the separator in file systems (often a portion corresponds to a file on a Unix server with exactly the same name):
Many Internet Relay Chat and in-game chat clients use the slash to distinguish commands, such as the ability to join or part a chat room or send a private message to a certain user. The slash has also been used in many chat mediums as a way of expressing an action or statement in the likeness of a command.
- /join #services – to join channel "#services"
- /me sings a song about birds.
The slash is used as a reply on instant messages representing "OK" or "check" or "got it" and also implying "thanks".
In Second Life chat the slash is used to select the communications channel allowing users to direct commands to various virtual objects listening on different channels (e.g. "/42 on" could be a message in local chat directing the house lights to turn on).
- In most programming languages, / is used as a division operator. Starting with version 2.2, Python uses // (two slashes) for integer division, rounding down.
- MATLAB and GNU Octave also have the ./ (a dot and a slash) to indicate an element-by-element division of matrices.
- Comments in C, C++, C#, Java, PHP, CSS, and SAS begin with /* (a slash and an asterisk), and end with */ (the same characters in the opposite order).
- C99, C++, C#, PHP, and Java also have comments that begin with // (two slashes) and span a single line.
- In SGML and derived languages such as HTML and XML, a slash is used to indicate a closing tag. For example, in HTML, </em> ends a section of emphasized text that had been started with <em>.
- Slashes are used as the standard delimiters for regular expressions, although other characters can be used instead.
- Slashes are sometimes used to show italics, when no special formatting is available. Example: /Italic text/
- IBM JCL uses two slashes to start each line in a batch job stream (except for /* and /&).
- Windows, DOS, CP/M, OpenVMS, and OS/2 all use the slash to indicate command-line options. For instance the "wide" option is added to the dir command by typing "dir/w" (no space is necessary). Compatibility with this is why DOS added the backslash path separator, because otherwise one could not run a program in a different directory, since the program name always ended at the slash.
The GEDCOM Standard for exchanging computerized genealogical data uses slashes to delimit surnames. Example: Bill /Smith/ Jr.
Slashes around surnames are also used in Personal Ancestral File.
Certain shorthand date formats use / as a delimiter, for example "16/9/2003" 16 September 2003.
In the UK there used to be[when?] a specialised use in prose: 7/8 May referred to the night which starts the evening of 7 May and ends the morning of 8 May, totalling about 12 hours depending on the season. This was used to list night-bombing air-raids which would carry past midnight. Some police units in the USA use this notation for night disturbances or chases. Conversely, the form with an en dash, 7–8 May, would refer to the two-day period, at most 48 hours. This would commonly be used for meetings.
ISO 8601 provides a standard method of expressing dates and times which resolves ambiguities caused by the different formats historically used by different countries. According to this norm, dates must be written year-month-day using hyphens, but time periods are written separated by a solidus: 1939-09-01/1945-05-08, for example, would be the duration of the Second World War in the European theatre, while 2010-09-03/12-22 might be used for the autumn term of a northern-hemisphere school, from September the third to December the twenty-second, both in 2010. Instead of the solidus in some applications a double hyphen is used, e.g. 1939-09-01--1945-05-08, which would allow the use of the duration in filenames.
The slash has been used as the title of a novel by Greg Bear, / (Slant). The "Slant" was added on to give people something to call the book, but it has ultimately become the accepted title in many book lists.
The slash is also the symbol for a wand in NetHack.
Library science 
In cataloging, as prescribed by the Anglo-American Cataloguing Rules, a slash is used to separate the title from the statement of responsibility (e.g., author, director, production company). The slash is flanked by a single space on either side. This form may be seen on catalog cards as well as electronic catalogs, depending on how items are chosen to display.
- Gone with the Wind / by Margaret Mitchell.
- Star Trek II. The Wrath of Khan [videorecording] / Paramount Pictures.
Slashes (or virgules) are used in addresses of places. E.g. 8/A Pushkar Society, to specify the eighth Apartment (bearing Number 8) in Building A of a multi-building residential complex named Pushkar Society. However, 8-A or # 8A will mean Section or Wing A of Apartment 8. In this sense, the slash stands for of.
Slashes (or virgules) are used to indicate the serial number of an article in a set of a finite number of articles. E.g. "page #17/35" in a document indicates the seventeenth out of a total of 35 pages in a document/chapter/book. Also, the marking "#333/500" on one of many packages indicates that the package so identified is three hundred thirty-third out of 500 numbered packages. In this sense, the slash stands for "out of".
Slashes (virgules) are used in music 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 quantum field theory, a slash through a symbol, such as ⱥ, is shorthand for γμaμ, where a is a covariant four-vector, the γμ are the gamma matrices, and the repeated index μ is summed over according to the Einstein notation.
Other alternations with hyphen 
Besides the varied usage with dates, the slash is used to indicate a range of serial numbers which have the hyphen already as part of their alphanumeric symbol set. The primary example is the US Air Force serial numbers for aircraft. These are usually written, for example, as "85-1000", for the thousandth aircraft ordered in fiscal year 1985. To designate a series of serial numbers, the slash is used, as in 85-1001/1050 for the first fifty subsequent aircraft.
Gender-neutrality in Spanish and Portuguese 
In Portuguese and Spanish, as well in other West Iberian languages, many feminine forms are very similar to the masculine ones, differing only by an extra desinence, usually an "-a". For instance, the feminine of "pintor" ("male painter" both in Spanish and Portuguese) is "pintora". These two forms can be joined together through a slash: pintor/a. Proponents of gender-neutral language assert that this composed form should be used when the sex of the person referred to is unknown or when a description fits both sexes. Traditionally, speakers of these languages (and others from the Romance family) employ the masculine form in this sense, even when the description is also suitable for a woman.
Although parentheses are longer and less specific than a slash, they are the preferred punctuation marks in Portuguese, so "painter" (meaning male or female) is usually written as "pintor(a)". Prominent Portuguese grammar references don't mention any use of the slash, but at least one proposal of gender-inclusive Portuguese does incorporate the sign. According to Portuguese With Inclusion of Gender, a slash should be used instead of parentheses. Slashes should not be used when an at-sign ("@") or an a-e ligature ("æ") are more appropriate.
Alternative names 
- diagonal (rare)
- forward slash
- forward stroke
- fraction bar or just bar
- over when the symbol is used to indicate division
- per when used to indicate prices (e.g., $5/dozen, read, "five dollars per dozen")
- right-leaning stroke
- scratch comma
- slak (rare)
- slat (rare)
- solidus, or shilling mark (may be more slanted than the slash)
- stroke In British English this is often used when reading the character aloud, although this term is also used to mean any single mark or dash in general. It is common to hear someone say "this stroke that", whereas a North American speaker is more likely to say "this slash that". However, the term slash is usually used in the UK when reading computer pathnames. Stroke is also commonly used among the North American amateur radio community.
- virgula suspensiva
- whack Some speakers use this term only for the backslash ("\").
- Bringhurst, Robert (2002). The Elements of Typographic Style. Publisher: Hartley & Marks Publishers; 2nd edition (2002). ISBN 978-0-88179-132-7. page 81-82
- "C0 Controls and Basic Latin. Unicode ASCII Punctuation code chart" (PDF). Unicode, Inc. 2010. p. 4.
- "General punctuation". Unicode.org. Retrieved 29 April 2013.
- "Unicode Character Encoding Stability Policy". Unicode.org. 2012-12-13. Retrieved 2013-04-29.
- "General Punctuation. Unicode General Punctuation code chart" (PDF). Unicode, Inc. 2010. p. 5.
- The Unicode Standard, Version 6.0.0. Addison-Wesley Professional. 2010. pp. p212. ISBN 978-0-321-48091-0.
- "Mathematical Operators. Unicode Mathematical Operators code chart" (PDF). Unicode, Inc. 2010. p. 3.
- Turton, Stuart. "Berners-Lee: web address slashes were 'a mistake'". PC Pro. October 15, 2009
- Cunha & Cintra (2001). Nova Gramática do Português Contemporâneo, 3rd edition revised. Rio de Janeiro, Nova Fronteira. ISBN 85-209-1137-4
- "Coleção NÚMEROS POLÊM iCOS" (PDF) (in Portuguese). Archived from the original on 2011-07-14. Retrieved 29 July 2012.
- Robson Fernando de Souza (2004-02-27). "Consciência Efervescente: A proposta do Português com Inclusão de Gênero". Conscienciaefervescente.blogspot.com. Retrieved 2012-07-24.
- "Free On-Line Dictionary of Computing". Foldoc.org. Retrieved 2012-07-24.
- Authors' and Printers' Dictionary, p. 371, READ BOOKS, 2007
- "Dictionary.com". Dictionary.reference.com. Retrieved 2012-07-24.
- "ASCII". Catb.org. Retrieved 2012-07-24.
- Oxford Dictionaries FAQ[dead link]
- "stroke", Dictionary (Merriam-Webster online), retrieved 2011-10-18
- Truss, Lynne (2004). Eats, Shoots & Leaves: The Zero Tolerance Approach to Punctuation. New York: Gotham Books. p. 73. ISBN 1-59240-087-6.
- "Whack". Computerhope.com. Retrieved 2012-07-24.
- "Jargon file page on ASCII". Catb.org. Retrieved 2012-07-24.
- Klein, Samuel John (2006-03-03). Typography Words of the Day: Slashes. Designorati, 3 March 2006. Retrieved from designorati.com
- Gender-inclusive use of "/" in Portuguese (and in Spanish too): 2 - A língua e o sexo (2 - Language and Sex), Quartos (quarters) I, II and III, one of the subjects of Controversial Numbers project