The slash is a slanting line punctuation mark, . It is also known as a stroke or solidus, a forward slash and several other historical or technical names. Once used as the equivalent of the modern period and comma, the slash is now used to represent division and fractions, as a date separator, in between multiple alternative or related terms, and to indicate abbreviation.
History
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 (, which was used as a full stop (also known as a period), scratch comma, and caesura mark. These historical usages were lost over time, with its role as a full stop eventually being lost to the low dot (), and the other two usages developing separately into distinct marks, the comma () and the 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 before being usually simplified into various single dashes.
In the 18th century, the mark was generally known in English as the "oblique", particularly the less-vertical fraction slash. 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 a notation or abbreviation for the shilling. The name "slash" is a recent development, not appearing in Webster's Dictionary until the Third Edition (1961)Compare with but has gained wide currency through its use in computing, a context where it is sometimes used in British English in preference to "stroke". Clarifying terms such as "forward slash" were coined because MS-DOS and Windows use the backslash extensively.
Usage Disjunction and conjunction
Connecting alternatives
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/) and etymologies (e.g., F. /LL. /L. /PIE. ).
Such slashes may be used to avoid taking a position in naming disputes. One example is the Assyrian 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, is a son and a is a daughter; some proponents of gender-neutral language advocate the use of , or when writing for a general audience or addressing a listener of unknown gender. Less commonly, at sign is used instead: . Similarly, in German and some Scandinavian and Baltic languages, refers to any secretary and to an explicitly female secretary; some advocates of gender neutrality support forms such as for general use. This does not always work smoothly, however: problems arise in the case of words like ('doctor') where the explicitly female form is umlauted and words like ('Chinese person') where the explicitly female form loses the terminal -e.
Although not as common as brackets, slashes can also be used for uncertain plurals such as "child/ren", "is/are", "book/s", "answer/s" or "fix/es".
Connecting non-contrasting items The slash is also used as a shorter substitute for the conjunctions and and 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.
Presenting routes The slash, as a form of inclusive or, is also used to punctuate the stages of a route (e.g., Shanghai/Nanjing/Wuhan/Chongqing as stops on a tour of the Yangtze).
Introducing topic shifts 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.
In speech Sometimes the word slash is used in speech as a conjunction to represent the written role of the character (as if a written slash were being read aloud from text), e.g. "bee slash mosquito protection" for a beekeeper's net hood, and "There's a little bit of nectar slash honey over here, but really it's not a lot." (said by a beekeeper examining in a beehive),YouTube video "Drone laying hive building up and getting new equipment" at time 9:16 and "Gastornis slash Diatryma" for two supposed genera of prehistoric birds which are now thought to be one genus.
Mathematics
Fractions
The slash is used between two numbers to indicate a fraction or ratio. 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. Nowadays fractions, unlike inline division, are often given using smaller numbers, superscript, and subscript (e.g., /). 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.
This notation can also be used when the concept of fractions is extended from numbers to arbitrary rings by the method of localization of a ring.
Division The division slash is used between two numbers to indicate division. 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, Page 84 in this version who wrote: The occurrence of fractions, such as , , in the verbal part of mathematical works is a source of considerable loss of room, and creates an inelegant and even confused appearance in the printed page. It is very desirable, in every point of view, except the strictly mathematical one, that some method of representation should be adopted which does not require a larger space than is usual between two successive lines. At the same time, it is by no means of very great importance that the verbal part should entirely coincide with the mathematical part in notation, so long as the latter remains to preserve the usual conventions. The symbol ÷ has been disused for a sufficient reason, namely, the number of times which the pen must be taken off to form it. This has been, and we imagine always will be, the cause either of abandonment or abbreviation. The question is, whether a new and easy notation could not be substituted; and it is desirable that it should be derived from analogy, such as (accidentally, we believe) does exist in >, =, and <. If we look at × and +, and observe that the first is made by turning the second through half a right angle, denoting multiplication, which is primarily an extension of addition in like manner as division is an extension of subtraction, we may thus invent the symbol / or \ to denote division, which is also the symbol of subtraction turned through half a right angle. If a/b were used to denote a divided by b, and (a+b)/(c+d) to denote a + b divided by c + d, all necessity for increased spacing would be avoided; but this alteration should not be introduced into completely mathematical expressions, though it would be convenient in particular cases.
Quotient of set 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.
Combining slash 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 'element 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.
Computing The slash, sometimes distinguished as "forward slash", is used in computing in a number of ways, primarily as a separator among levels in a given hierarchy, for example in the path of a filesystem.
File paths