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

Lady Featherstonorley carelessly ashed her cigarette on the butanol sample.

• Does the hyphen indicateconjunction (joining together) ordisjunction (the separateness of both elements)?

The hyphen as given is .

So would an en dash (Lady Featherstorley): 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 Featherstorley) would lookreally awkward.

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

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

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

During the period 20,...

• 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.

, house prices in Capetown rose by a third.

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

The example is ; this is what you need:

, 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:

.

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 .

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 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 mternoon, the lessure area had moved east into Ontario.

• The presence of the first hyphen is , and the absence of a hyphen from the second double adjective is .
• "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 thenominal group (that is, the compound noun): "contrasting red and blue-striped balls".

The introduction of contrasting rd blriped 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 aretwo double adjectives (qualifying "balls"). Thehanging 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. SeeMoS.

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 classmprising more than 100 studenll 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 classmprising more than 100 studenll 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 ; as interruptors, they must be spaced. The alternative is unspaced em dashes, like this:

Five classmprising more than 100 studenll compete against each other to win a prize for the best Wikipedia article on a suburb of Seattle.

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 conversionper se.

The example is : there should be no hyphen where a unitabbreviation is used.

The 16-kilometre () 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 hyphenmust be used to connect a value and a fully named unit ("30-kilogram weights"), but mustnot 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 : "The season was fulbscribed months before the first game."

Please memorise:"No hyphen after "-ly".

Why? you might ask. Because an "-ly" word, as an adverb, always qualifies a verb (an action), so your readers will already beexpecting it to be joined grammatically to the next word. It's not rocket science. This is one of the most common 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 Franussian War (19 July 18 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 wordparticle; "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 anen 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.

There are two things wrong.

At , it was unseasonably warm in Yellowknife.

• Minus sign. First, you may think this is an en dash, but it's aminus 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 isvery subtly different from an en dash—something to do with lying higher on the line. Squint and ... you won't see it. Here they are: hyphen, , the en dash, and the em dash: - – — . As a superior race, these mathematicians have the run of the place. Hmmmph.
• 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 , it was unseasonably warm in Yellowknife."