Wikipedia:Manual of Style/Dash draft

The following is a draft revised text for the wording of the "Dashes" section of the Manual of Style (WP:DASH). It is based on the interim results of polling at WT:Manual of Style/dash drafting and related discussion at WT:Manual of Style/dash drafting/discussion.

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Dashes
Wikipedia uses two kinds of dashes: en dashes (–) and em dashes (—). Many keyboards lack both dashes, but there are several ways to enter them; see How to make dashes.

En dashes may be either spaced (i.e. having a space before and after the dash) or unspaced, depending on their function (see below). The space before a spaced dash should preferably be a non-breaking space. Em dashes are not spaced.

Dashes have the following uses:
 * 1) Unspaced em dashes or spaced en dashes are used to indicate interruption in a sentence.
 * 2) * In this use, on any one page, either use unspaced em dashes consistently, or use spaced en dashes consistently. Do not switch from one style to the other without good reason.
 * 3) * The dash indicates a sharp break in the flow of a sentence—sharper than is provided by a colon or a semicolon.
 * 4) * When the sentence returns to its original course, as in (Wikipedia—one of the most popular web sites—has the information you need), the pair of dashes marks part of the sentence as parenthetical; the two dashes are more arresting than a pair of commas, and less disruptive than parentheses.
 * 5) *This use of the dash is useful where there are already several commas; dashes can clarify the structure, sometimes removing ambiguity. However, use such dashes sparingly. They are visually striking, so two in a paragraph is often a good limit. Ensure also that use of multiple dashes does not introduce ambiguity.
 * 6) En dashes are used to stand for to or through in ranges: pp. 211–19, 64–75%, the 1939–45 war. In this use:
 * 7) *The dash is usually unspaced, but if the elements being linked themselves contain spaces (as with full dates), then the dash is spaced. For example, June 3, 1888 – August 18, 1940 and December 1989 – March 1990 (but 3–9 June 1969 and June–August 1940); 10 W – 100 kW (but 25–30 mm).
 * 8) *Do not combine dashes with other prepositions: from 450 to 500 people or between 450 and 500 people, not from 450–500 people or between 450–500 people.
 * 9) *Do not use dashes in ranges that involve a negative value, or in other contexts where they might be misconstrued as a minus sign: &minus;10 to 10, not &minus;10–10.
 * 10) Unspaced en dashes are used between numbers with the sense of to, in sports results and similar: a 4–3 win, they voted 5–4 in favour.
 * 11) Unspaced en dashes can be  used, in place of a hyphen, in compounds whose elements themselves contain hyphens or spaces (the anti-conscription–pro-conscription debate, the New York–Sydney flight; the New Zealand–South Africa grand final) and when joining a prefix to an element containing a space (pre–World War II technologies, ex–prime minister), but usually not when joining a prefix to a hyphenated element (non-government-owned corporations, semi-labor-intensive industries). Such constructions are often  clumsy;  the conscription debate, technologies from before World War II, or former prime minister  are generally preferable to compounding.
 * 12) It is often preferable to substitute an unspaced endash for a hyphen in compound modifiers (see under "Hyphens" above) in which the parts of the compound are independent and equal elements. The dash may stand for and, or, versus, to, between...and, and so on. Examples: diode–transistor logic, Michelson–Morley experiment, Seifert–van Kampen theorem, male–female ratio, Lincoln–Douglas debate, French–German border. An en dash is not used for a hyphenated personal name (Lennard-Jones potential, named after John Lennard-Jones), nor for a hyphenated place name (Guinea-Bissau), nor with an element that lacks lexical independence (like the prefix "Sino-" in Sino-Japanese trade).
 * 13) Spaced en dashes may optionally be used as separators, such as between parts of names or titles (Harry Potter and the Deathly Hallows – Part 1, although a colon can also be used here) or between elements of list items or table entries (for example, in track listings in articles about music albums, spaced en dashes may be used between track titles and durations).

Agreement between article titles and article text is desirable; Wikipedia's policy on article titles is at Article titles.