User:Dicklyon/dashes

Trying a more Cambridge-style approach...

Dashes and long hyphens
Two distinct grammatical punctuation symbols, the dash and the long hyphen, are usually realized in Wikipedia style by the two characters called em dash and en dash (also known as em rule and en rule), respectively, though the dash punctuation is sometimes realized by a spaced en dash as a stylistic alternative. In other styles, such as typewritten text, the long hyphen is realized by the ordinary hyphen (the hyphen-minus character), and the dash by a pair of hyphens. The term long hyphen was introduced in The Cambridge Grammar of the English Language to describe the logical role as a punctuation indicator, to separate it from the term for the character that realizes the puncutation, which may be the en dash or the hyphen in different styles; most sources just refer to the en dash, or sometimes the en rule, for the roles that we describe here for the long hyphen.

See WP:How to make dashes or the article on dashes for common input methods for these characters.

Dashes should never be used in the filenames of images; use hyphens instead. Where a dash is used in an article or category's title, there should be a redirect from the version with a hyphen.

Long hyphens
Long hyphen, realized in Wikipedia by en dashes (–, &amp;ndash;), have several distinct roles.


 * 1) To stand for to or through in ranges (pp. 211–19, 64–75%, the 1939–45 war). Ranges expressed using prepositions (from 450 to 500 people or between 450 and 500 people) should not use dashes (not from 450–500 people or between 450–500 people). Number ranges must be spelled out if they involve a negative value or might be misconstrued as a subtraction (&minus;10 to 10, not &minus;10–10).
 * 2) To stand for to or versus (male–female ratio, 4–3 win, Lincoln–Douglas debate, France–Germany border).
 * 3) To stand for and between independent elements (diode–transistor logic, Michelson–Morley experiment). An en dash is not used for a hyphenated personal name (Lennard-Jones potential, named after John Lennard-Jones), nor a hyphenated place name (Guinea-Bissau), nor with an element that lacks lexical independence (the prefix Sino- in Sino-Japanese trade).
 * 4) To separate items in a list—for example, in articles about music albums, en dashes are used between track titles and durations, and between musicians and their instruments. In this role, en dashes are always spaced.
 * 5) In compounds whose elements themselves contain hyphens or spaces (the anti-conscription–pro-conscription debate) and when prefixing an element containing a space (pre–World War II technologies, ex–prime minister) – but usually not when prefixing an element containing a hyphen (non-government-owned corporations, semi-labor-intensive industries). However, recasting the phrase (the conscription debate, technologies prior to World War II) may be better style than compounding.
 * 6) As a stylistic alternative to em dashes (see below).


 * Spacing

Disjunctive en dashes are unspaced, except when there is a space within either one or both of the items (the New York – Sydney flight; the New Zealand – South Africa grand final; June 3, 1888 – August 18, 1940, but June–August 1940). Exceptions are occasionally made where the item involves a spaced surname (Seifert–van Kampen theorem).

The space before an en dash should preferably be a non-breaking space.


 * En dashes in article titles

When naming an article, do not use a hyphen as a substitute for an en dash that properly belongs in the title, for example in Eye–hand span. To aid searching and linking, provide a redirect from the corresponding article title with hyphens in place of en dashes, as in Eye-hand span.

Dashes
Dashes, realized in Wikipedia by em dashes (—, &amp;mdash;), indicate interruption in a sentence or list. They are used in two roles.


 * 1) Parenthetical (Wikipedia—one of the most popular web sites—has the information you need). A pair of em dashes for such interpolations is more arresting than a pair of commas, and less disruptive than round brackets.
 * 2) As a sharp break in the flow of a sentence—sharper than is provided by a colon or a semicolon.


 * In both roles, em dashes are useful where there are already several commas; em dashes can clarify the structure, sometimes removing ambiguity.
 * Use em dashes sparingly. They are visually striking, so two in a paragraph is often a good limit. Ensure there is no ambiguity if using multiple "sharp break" or parenthetical em dashes in the same area of the text.
 * Do not space em dashes.


 * Spaced en dashes as an alternative to em dashes


 * Spaced en dashes – such as here – can replace unspaced em dashes in all of the ways discussed above. Several major publishers use spaced en dashes to the complete exclusion of em dashes. Use one style consistently throughout an article.

Other dashes
Do not use substitutes for em or en dashes, such as the combination of two hyphens (--). These were typewriter approximations.