The dash is a punctuation mark consisting of a long horizontal line. It is similar in appearance to the hyphen but is longer and sometimes higher from the baseline. The most common versions are the endash , generally longer than the hyphen but shorter than the minus sign; the emdash , longer than either the en dash or the minus sign; and the horizontalbar , whose length varies across typefaces but tends to be between those of the en and em dashes.
Typical uses of dashes are to mark a break in a sentence, to set off an explanatory remark—similar to parentheses—or to show spans of time or ranges of values.
The em dash is sometimes used as a leading character to identify the source of a quoted text.
History
In her book on ellipsis, Ellipsis in English Literature: Signs of Omission, Anne Toner suggests that the first dash that has been found in printed English is from a letter in 1580 and the first use of the dash in English drama dates to a 1588 translation of Terence's Andria, by Maurice Kyffin, where it is composed of a line of hyphens:
The popularity of dashes in drama took off after Kyffin's usage; there were three examples in his 1588 translation of Andria, but the 1627 translation of the same play had 29. They appear in William Shakespeare's plays in addition to Ben Jonson's. In the first folio edition of Shakespeare's Henry IV, Part 1, Toner writes, "Hotspur dies on a dash", with his last words cut short.
In 1634, John Barton, an English schoolmaster, wrote in The Art of Rhetorick that "eclipsis" is much used in playbooks "where they are noted thus ". Toner goes on to explain:
(The earliest example given in Ellipsis in English Literature of the mark nowadays called an ellipsis, , is dated to 1710.)
In the early 17th century, in Okes-printed plays of William Shakespeare, dashes are attested that indicate a thinking pause, interruption, mid-speech realization, or change of subject. The dashes are variously longer (as in King Lear reprinted 1619) or composed of hyphens (as in Othello printed 1622); moreover, the dashes are often, but not always, prefixed by a comma, colon, or semicolon.
Authors have sometimes had a negative view of the dash. In the 18th-century, Jonathan Swift rhymed "dash" with "printed trash", while Henry Fielding chose the name 'Dash' for an unlikeable character in his 1730 play The Author's Farce.
In 1733, in Jonathan Swift's On Poetry, the terms break and dash are attested for and marks:
Blot out, correct, insert, refine, Enlarge, diminish, interline; Be mindful, when Invention fails; To scratch your Head, and bite your Nails.
Your poem finish'd, next your Care Is needful, to transcribe it fair. In modern Wit all printed Trash, is Set off with num'rous Breaks⸺and Dashes—
On the topic of composing a dash out of a series of hyphens vs a single typographical rule, Toner observes:
The dash made of hyphens became less and less common with time until its resurgence with typewriter conventions.
Types of dash Usage varies both within English and within other languages, but the usual conventions for the most common dashes in printed English text are these: An (unspaced) em dash or a spaced en dash can be used to mark a break in a sentence, and a pair can be used to set off a parenthetical phrase. For example: An en dash, but not an em dash, indicates spans or differentiation, where it may replace "and", "to", or "through". For example: An em dash or horizontal bar, but not an en dash, is used to set off the source of a direct quotation. For example: A horizontal bar (also called quotation dash) or the em dash, but not the en dash, introduces quoted text. In informal contexts, a hyphen () is often used as a substitute for an endash, as is a pair of hyphens () for a long dash, because the hyphens symbol is readily available on most keyboards. The autocorrection facility of word-processing software often corrects these to the typographically correct form of dash.
Figure dash The figure dash () has the same width as a numerical digit (many computer fonts have digits of equal width). It is used within numbers, such as the phone number 555‒0199, especially in columns so as to maintain alignment. In contrast, the en dash () is generally used for a range of values.
The minus sign () glyph is generally set a little higher, so as to be level with the horizontal bar of the plus sign. In informal usage, the hyphen-minus (), provided as standard on most keyboards, is often used instead of the figure dash.
In TeX, the standard fonts have no figure dash; however, the digits normally all have the same width as the en dash, so an en dash can be a substitution for the figure dash. In XeLaTeX, one can use \char"2012. The Linux Libertine font also has the figure dash glyph.
En dash The en dash, en rule, or nut dash is traditionally half the width of an em dash. In modern fonts, the length of the en dash is not standardized, and the en dash is often more than half the width of the em dash. The widths of en and em dashes have also been specified as being equal to those of the uppercase letters N and M, respectively, and at other times to the widths of the lower-case letters.
Usage The three main uses of the en dash are:
to connect symmetric items, such as the two ends of a range or two competitors or alternatives to contrast values or illustrate a relationship between two things to compound attributes, where one of the connected items is itself a compound
Ranges of values The en dash is commonly used to indicate a closed range of values—a range with clearly defined and finite upper and lower boundaries—roughly signifying what might otherwise be communicated by the word "through" in American English, or "to" in International English.Lamb, David. "Hyphens, En Dashes, and Em Dashes: Correct Usage". Academic Writing Tutor. Retrieved 2 September 2013. This may include ranges such as those between dates, times, or numbers. Various style guides restrict this range indication style to only parenthetical or tabular matter, requiring "to" or "through" in running text. Preference for hyphen vs. en dash in ranges varies. For example, the APA style (named after the American Psychological Association) uses an en dash in ranges, but the AMA style (named after the American Medical Association) uses a hyphen:
En dash range style (e.g., APA) Hyphen range style (e.g., AMA) Running text spell-out June–July 1967 JuneJuly 1967 June and July 1967 1:15–2:15 p.m. 1:152:15 PM 1:15 to 2:15 p.m. For ages 3–5 For ages 35 For ages 3 through 5 pp. 38–55 pp 3855 pages 38 through 55 President Jimmy Carter (1977–81) President Jimmy Carter (197781) President Jimmy Carter, in office from 1977 to 1981
Some style guides (including the Guide for the Use of the International System of Units (SI) and the AMA Manual of Style) recommend that, when a number range might be misconstrued as subtraction, the word "to" should be used instead of an en dash. For example, "a voltage of 50 V to 100 V" is preferable to using "a voltage of 50–100 V". Relatedly, in ranges that include negative numbers, "to" is used to avoid ambiguity or awkwardness (for example, "temperatures ranged from −18°C to −34°C"). It is also considered poor style (best avoided) to use the en dash in place of the words "to" or "and" in phrases that follow the forms from X to Y and between X and Y.
Relationships and connections The en dash is used to contrast values or illustrate a relationship between two things. Examples of this usage include: Australia beat American Samoa 31–0. Radical–Unionist coalition Boston–Hartford route New York–London flight (however, it may be argued that New York–to–London flight is more appropriate because New York is a single name composed of two valid words [see "Attributive compounds" below]; with a single en dash, the phrase is ambiguous and could mean either Flight from New York to London or New flight from York to London; such ambiguity is assuaged when used mid-sentence, though, because of the capital N in "New" indicating it is a special noun). If dash–hyphen use becomes too unwieldy or difficult to understand, the sentence can be rephrased for clarity and readability; for example, "The flight from New York to London was a pleasant experience". Mother–daughter relationship The Supreme Court voted 5–4 to uphold the decision.
A distinction is often made between "simple" attributive compounds (written with a hyphen) and other subtypes (written with an en dash). Some sources consider name pairs where the paired elements carry equal weight, as in the Taft–Hartley Act, to be "simple"; others consider an en dash appropriate in instances such as these to represent the parallel relationship, as in the McCain–Feingold bill or Bose–Einstein statistics. However, there is a difference between something named for a parallel/coordinate relationship between two people for example, Satyendra Nath Bose and Albert Einstein and something named for a single person who had a compound surname, which may be written with a hyphen or a space but not an en dashfor example, the Lennard-Jones potential [hyphen] is named after one person (John Lennard-Jones), as are Bence Jones proteins and Hughlings Jackson syndrome. Copyeditors use dictionaries (general, medical, biographical, and geographical) to confirm the eponymity (and thus the styling) for specific terms, given that no one can know them all offhand.
When acts of the U.S. Congress are referred to by two of their sponsors, such as the Taft–Hartley Act or McCain–Feingold Act, it is common for news media to use an en dash between the names of the sponsors. However, when an act of the U.S. Congress is officially named using the surnames of the senator and representative who sponsored it, a hyphen is used in the short title; for example, the short title of Public Law 111–203 is the "Dodd-Frank Wall Street Reform and Consumer Protection Act", with a hyphen rather than an en dash between "Dodd" and "Frank".
Preference for an en dash instead of a hyphen in these coordinate/relationship/connection types of terms differs between style guides. For example, The American Heritage Dictionary of the English Language, the AMA Manual of Style, and Dorland's medical reference works use hyphens rather than en dashes in coordinate terms (such as "blood-brain barrier"), in eponyms (such as "Cheyne-Stokes respiration", "Kaplan-Meier method"), and so on. In other styles, such as AP Stylebook or The Chicago Manual of Style, the en dash is used to describe two closely related entities in a formal manner.
Attributive compounds In English, the en dash is usually used instead of a hyphen in compound (phrasal) attributives in which one or both elements is itself a compound, especially when the compound element is an open compound, meaning it is not itself hyphenated. This manner of usage may include such examples as: The hospital–nursing home connection (the connection between the hospital and the nursing home, not a home connection between the hospital and nursing) A nursing home–home care policy (a policy about the nursing home and home care) Pre–Civil War era Pulitzer Prize–winning novel New York–style pizza The non–San Francisco part of the world The post–World War II era (Compare post-war era, which, if not fully compounded (postwar), takes a hyphen, not an en dash. The difference is that war is not an open compound, whereas World War II is.) Trans–New Guinea languages The ex–prime minister a long–focal length camera water ice–based bedrock
The disambiguating value of the en dash in these patterns was illustrated by Strunk and White in The Elements of Style with the following example: When Chattanooga News and Chattanooga Free Press merged, the joint company was inaptly named Chattanooga News-Free Press (using a hyphen), which could be interpreted as meaning that their newspapers were news-free.