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.
History
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.
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—
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 statement. 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-minus () is often used as a substitute for an endash, as is a pair of hyphen-minuses () for an emdash, because the hyphen-minus 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. (Most 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 upper-case 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 valuesa range with clearly defined and finite upper and lower boundariesroughly signifying what might otherwise be communicated by the word "through" in American English, or "to" in International English. 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: