4 Punctuation

4.11 Dashes

4.11.1 En rule

The en rule (US en dash) (–) (Unicode code point U+2013 en dash) is longer than a hyphen and half the length of an em rule. (See 4.11.2 for a definition of an em). Many British publishers use an en rule with space either side as a parenthetical dash, but Oxford and most US publishers use an em rule.

Use the en rule closed up in elements that form a range:

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In specifying a range use either the formula from … to … or xxxx–xxxx, never a combination of the two (the war from 1939 to 1945 or the 1939–45 war, but not the war from 1939–45). For more on ranges see Chapter 11.

The en rule is used closed up to express connection or relation between words; it means roughly to or and:

Dover–Calais crossing

Ali–Foreman match

editor–author relationship

Permian–Carboniferous boundary

It is sometimes used like a solidus to express an alternative, as in an on–off relationship (see 4.13.1).

Use an en rule between names of joint authors or creators to show that it is not the hyphenated name of one person. Thus the Lloyd–Jones theory involves two people (en rule), the Lloyd-Jones theory one person (hyphen), and the Lloyd-Jones–Scargill talks two people (hyphen and en rule).

In compound nouns and adjectives derived from two names an en rule is usual:

  • Marxism–Leninism (Marxist theory as developed by Lenin)

  • Marxist–Leninist theory

although for adjectives of this sort a hyphen is sometimes used. Note the difference between Greek–American negotiations (between the Greeks and the Americans, en rule) and his Greek-American wife (American by birth but Greek by descent, hyphen). Elements, such as combining forms, that cannot stand alone take a hyphen, not an en rule: Sino-Soviet, Franco-German but Chinese–Soviet, French–German.

Spaced en rules may be used to indicate individual missing letters:

  • the Earl of H – – w – – d

  • ‘F – – – off!’ he screamed

The asterisk is also used for this purpose (see 4.15).

4.11.2 Em rule

The em rule (US em dash) (—) (Unicode code point U+2014 em dash) is twice the length of an en rule. (An em is a unit for measuring the width of printed matter, originally reckoned as the width of a capital roman M, but in digital fonts equal to the current typesize, so an em in 10 point text is 10 points wide.) Oxford and most US publishers use a closed-up em rule as a parenthetical dash; other British publishers use the en rule with space either side.

No punctuation should precede a single dash or the opening one of a pair. A closing dash may be preceded by an exclamation or question mark, but not by a comma, semicolon, colon, or full point. Do not capitalize a word, other than a proper noun, after a dash, even if it begins a sentence.

A pair of dashes expresses a more pronounced break in sentence structure than commas, and draws more attention to the enclosed phrase than brackets:

  • The party lasted—we knew it would!—far longer than planned

  • There is nothing—absolutely nothing—half so much worth doing as simply messing about in boats

Avoid overuse of the dash in this context and the next; certainly, no more than one pair of dashes should be used in one sentence.

A single parenthetical dash may be used to introduce a phrase at the end of a sentence or replace an introductory colon. It has a less formal, more casual feel than a colon, and often implies an afterthought or aside:

  • I didn’t have an educated background—dad was a farm labourer

  • Everyone understands what is serious—and what is not

  • They solicit investments from friends, associates—basically, anyone with a wallet

Do not use it after a colon except in reproducing antique or foreign-language typography.

Use an em rule spaced to indicate the omission of a word, and closed up to indicate the omission of part of a word:

  • We were approaching — when the Earl of C— disappeared

Asterisks or two or more en rules are also employed for this purpose (see 4.11.1, 4.15).

An em rule closed up can be used in written dialogue to indicate an interruption, much like an ellipsis indicates trailing off:

  • ‘Does the moon actually—?’

  • ‘They couldn’t hit an elephant at this dist—’

A spaced em rule is used in indexes to indicate a repeated word (see Chapter 19). Two spaced em rules (—) are used in some styles (including Oxford’s) for a repeated author’s name in successive bibliographic entries (see Chapter 18).

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New Hart's Rules