User:Tony1/How to use hyphens and dashes

Lady Featherstone-Morley carelessly ashed her cigarette on the butanol sample.

Lady Featherstone-Morley carelessly ashed her cigarette on the butanol sample.

• Does the hyphen indicate conjunction (joining together) or disjunction (the separateness of both elements)?

The hyphen as given is correct.

So would an en dash (Lady Featherstone–Morley): there's no opposition or particular relationship between the names here, other than their coming together into someone's compound name.

An em dash (Lady Featherstone—Morley) would look really awkward.

During the period 2005-07, the number of articles on the English Wikipedia quadrupled.

During the period 2005-07, the number of articles on the English Wikipedia quadrupled.

The hyphen is incorrect. Here, there's a year range, requiring an en dash, which stands for "to":

During the period 2005–07,...

• If the reader is already familiar with what you're saying, you might even drop "the period".
• Many people prefer just two closing digits, as here, to the full expression ("2005–2007"). MOSNUM says that one and three closing digits are unacceptable.

From 2005–07, house prices in Capetown rose by a third.

From 2005–07, house prices in Capetown rose by a third.

• There's something inconsistent in the coloured text. Say it aloud.

The example is incorrect; this is what you need:

From 2005 to 2007, house prices in Capetown rose by a third.

• The en dash stands for "to", and that's how you'll vocalise it in reading it aloud. We need both prepositions spelled out: "from ... to", not "from ... –", which is awkward.
• Either that, or recast it:

In (or "During") the period 2005–07.

The same applies to "between". Remember, "from" and "between".

The case was upheld by the Supreme Court in a 4–3 judgement.

What word could be substituted for the symbol?

The en dash is correct.

An en dash can stand for "to", "against" or "versus"—these functions are all disjunct (indeed, adversarial) relationships between the items, so a squashy little hyphen (a 4-3 judgement) would be wrong. It's the same for sports scores: "The Vancouver Canucks massacred the New York Islanders in an 11–2 victory" (not "an 11-2 victory").

By mid-afternoon, the low pressure area had moved east into Ontario.

Double adjectives often require hyphenation; and there's another issue. No en dashes this time.

By mid-afternoon, the low-pressure area had moved east into Ontario.

• The presence of the first hyphen is correct, and the absence of a hyphen from the second double adjective is incorrect.
• "Mid-" anything is usually hyphenated by convention, probably because "mid" itself isn't a whole word, yet doesn't jam into the noun nicely the way some prefixes do.
• "Low-pressure area"—the noun is "area", qualified by a double adjective. There's no such thing as a "pressure area", which could be low or high. Same for "upper-level jet stream"; it's not a "level jet stream" that happens to be the upper one of two.
• What about "the area of low pressure over the coast"—shouldn't it be "an area of low-pressure"? Nope. There's no double adjective, so no hyphen should be used: here, "low" is an adjective; "pressure" is a noun.

The introduction of contrasting red and blue–striped balls transformed the game.

Two things wrong: the type of symbol, and the need for it in another place as well. Think of the nominal group (that is, the compound noun): "contrasting red and blue-striped balls".

The introduction of contrasting red- and blue-striped balls transformed the game.

There were two problems:

• Hyphen, not en dash. An en dash was being used to conjoin two adjectives; this job is reserved for hyphens.
• Hanging hyphen. Not just "blue", but "red" requires a hyphen to link it to the coupled word "striped"; there are two double adjectives (qualifying "balls"). The hanging hyphen added to "red" is useful for making this double compound expression neater. It's a rare case in which a hyphen is followed by a space. See MoS.

Five classes–comprising more than 100 students–will compete against each other to win a prize for the best Wikipedia collaboration on an article on their chosen suburb of Seattle.

• Five classes–comprising more than 100 students–will compete against each other to win a prize for the best Wikipedia article on a suburb of Seattle.
• These en dashes are "interrupters", like very strong commas; they usually occur in pairs to mark off explanatory text.

Five classes – comprising more than 100 students – will compete against each other to win a prize for the best Wikipedia article on a suburb of Seattle.

The en dashes are required, but their formatting is incorrect; as interruptors, they must be spaced. The alternative is unspaced em dashes, like this:

Five classes—comprising more than 100 students—will compete against each other to win a prize for the best Wikipedia article on a suburb of Seattle.

But decide at the start of a text which one you'll use as interruptors: closed em dashes or open en dashes. It must be consistent (though keep the original in quotes).

The 16-kilometre (10-mi) distance between the centres has been a major impediment to economic development.

There's nothing wrong with the choice of units or the fact of the conversion per se.

The example is incorrect: there should be no hyphen where a unit abbreviation is used.

The 16-kilometre (10 mi) distance between the centres has been a major impediment to economic development.

Sure, both main unit and conversion are used as double adjectives, describing "distance". But the ISO rules, which WP agrees with in this case, are that a hyphen must be used to connect a value and a fully named unit ("30-kilogram weights"), but must not connect a value and an abbreviated unit ("30 kg weights"). Fussy, isn't it.

The season was fully-subscribed months before the first game.

What is the hyphen trying to do? Is "fully", as an adverb, always going to be clearly and easily connected with a subsequent verb? (Yes.)

The hyphen is incorrect: "The season was fully subscribed months before the first game."

Please memorise: '"No hyphen after an "-ly"' adverb.

Why? you might ask. Because an "-ly" word, as an adverb, always qualifies a verb (an action), so your readers will already be expecting it to be joined grammatically to the next word. It's not rocket science. This is one of the commonest hyphen glitches on Wikipedia.

The Franco–Prussian War (19 July 1870—10 May 1871) resulted in a complete victory for the Prussians and foreshadowed the unification of Germany.

Both dashes are wrong; why?

The Franco-Prussian War (19 July 1870 – 10 May 1871) resulted in a complete victory for the Prussians and foreshadowed the unification of Germany.

• Word particle. A hyphen should be used in favour of an en dash between two items if one item (or both) is just a word particle; "Franco-" is such a particle – a mere prefix – whereas "French" would be the full-word equivalent ("the French–Prussian War", with an en dash; but by convention this is not the expression). Same for "Sino-Russian War", as opposed to "Chinese–Russian trade agreement". An acronym or abbreviation in this context would count as a full word ("the recent UK–Iceland spat over financial matters").
• Range. The em dash in the date was wrong: ranges require an en dash, and if either item has an internal space, as in both dates here, the en dash must also be spaced, on both sides. Many editors use a non-breaking space on the left side of the en dash when it's spaced ("... July 1870 – 10 May ...").

At -25°C it was unseasonably warm in Yellowknife.

Two things are wrong.

At −25 °C, it was unseasonably warm in Yellowknife.

• Minus sign. First, you may think this is an en dash, but it's a minus sign, which mathematicians are fussy about. Until early 2008, MOS used to allow en dashes for negative signs (−3.5) and subtraction operators (4 − 1 = 3); not any more. A minus sign is very subtly different from an en dash—it lies higher on the line. Here they are: hyphen, minus sign, the en dash, and the em dash: - − – — .
• Value–unit space. Second, MOS insists on a space between all values (−25) and units (°C), with two minor exceptions (angular degrees and geographical coordinates); so it's −25 °C, not −25°C. There's no space between the minus sign and the value (never − 25)
• Keying it in. Take a look at how you should key it in: "At −25 °C, it was unseasonably warm in Yellowknife."