Hyphens

Hyphens exist to make sentences clear and to avoid ambiguity. See the difference in meaning between these pairs:

He was a black cab driver. / He was a black-cab driver.Look, a man eating shark. / Look, a man-eating shark.The two year-old machines were replaced. / The two-year-old machines were replaced.

When to use them

Where two or more words precede and describe a noun (a noun is a thing, object or concept, such as cost, phone, car):

set-up costs pay-as-you-go phoneseven-seat carslow-moving vehiclelong-term projectbuilt-in features

Note that this only applies if the description comes before the noun. If it comes after (for example “the car has seven seats” or “the satnav is built in”), you don’t need a hyphen.

Use them with adverbs such as ill, much, well:

We think this was an ill-informed decisionThe model has been given a much-needed redesignThis is a well-respected brand

However, here too the hyphen is not needed if the description comes after the noun: eg “We think this decision was ill informed.”

Use hyphens when writing out ages in full, whether followed by a noun or not: a 10-year-old boy, a 10-year-old. Note that two hyphens are needed – it’s a seven-month-old son, not a seven-month old son.

Use them when they are necessary for sense and pronunciation, such as when the same letter would otherwise be repeated:

co-operation (not cooperation)pre-empt (not preempt)mis-sell (not missell)

When not to use them

Hyphens are only needed where they aid understanding and clarity, so most of the time you should be able to judge whether you need one just by re-reading your sentence. They’re pretty ugly, so don’t use one if you don’t need to.

Our style is to omit them for well-known expressions where the meaning is clear:

high street storeenergy efficiency ratinghome cinema systemfinancial services sectorice cream maker

In line with other modern publications, we usually omit hyphens for prefixes such as multi, over, under, so multimedia, multinational, multistorey, oversupply, oversubscribed, underperform

This also applies to re and pre, so redecorate, revamp, prepaid etc.

Don’t use a hyphen where a word ends in ly. There is no need, as they cannot be misinterpreted. So:

a highly respected barrister – not a highly-respected barristera sorely needed modification – not a sorely-needed modification

Nouns, verbs and adjectives

Often the need to hyphenate depends on how the words are being used. Hence:

First you need to log in (verb), enter your log-in details (adj), you’ll be asked to provide your age at login (noun).

The machine is easy to set up (verb), set-up costs are low (adj), keep the manual handy during setup (noun).

Dashes

It is almost always better to use commas (and sometimes even brackets) than dashes. It’s clearer and it doesn’t create ugly gaps on the page. Save dashes for when you have something truly astounding to say, which warrants the pause that a dash creates.

The following is pinched directly from The Times’s style guide (with permission). It sums it up nicely:

“While - on occasion - an effective device, they can quickly - and frequently - become ugly and tiresome. As a rule of thumb, one pair per 500 words is enough.”

In the following cases (exciting or shocking information), dashes are justified:

“The manufacturer claims this model makes deep-fat frying safer - but we found it made it three times more dangerous.”

“We found that you could save yourself hours of work – not to mention more than £50 – by steering clear of this service.”

In the following cases (essential but not exciting information) it would be better to replace them with commas or rephrase the sentence:

“This model – which is available at Argos – scored well in our tests.” Use commas instead.

“This model is cheaper – at £80 – than many of its rivals.” Rephrase as “At £80, this model is cheaper than many of its rivals.”