There are three dashes that you need to know. They’re of different lengths. Let’s size them up.
Hyphen –
en-dash –
em-dash —
The hyphen
At its best, the humble little hyphen can punch above its weight in the war on ambiguity. For example:
- Janice is a small arms dealer.
- Cesare is a hot pool attendant.
Is Janice petite, or does she trade pistols? Does Cesare work at the thermal baths, or does he have pecs appeal? Without hyphens in ‘small-arms’ and ‘hot-pool’, who’s to know?
Beyond these more clear-cut tidy-ups, hyphenation can be a fuzzy issue. Some writers love them, others hate them. Winston Churchill called the hyphen ‘a blemish to be avoided wherever possible’ – which is a bit rich, considering his full surname.
It helps to follow the rule of hyphenating before the noun. A real-estate agent. A camp-oven salesman. A dead-funny comedienne. (Adverbs ending in ‘-ly’ are an exception: there’s no hyphen required in ‘closely observed trains’.) But ultimately it comes down to readability. For all I care, you can have ‘much loved aunt’, over ‘much-loved aunt’, because there’s no ambiguity. And yet ambiguity is hard to spot in your own writing, however many times you reread it, which is why it’s good to employ a proofreader. Just sayin’.
The en-dash
The en-dash is the Goldilocksian bear, the one in the middle. It has two main uses. It serves as a substitute for an omitted conjunction, and it can mark off a parenthetical clause (as can the em).
1) The en as a substitute
As a stand-in for ‘to’, signifying a span:
- Winston Leonard Spencer-Churchill (1874–1965) hated hyphens.
- Iggy Pop (1947–) fronted the Stooges.
- See pages 34–55.
- I left my favourite hat on the Masterton–Wellington train.
- Lost property is open daily, 2–4 p.m.* * Please, please avoid the following construction: ‘Lost property is open daily, from 2–4 p.m.’ If you use ‘from’, it absolutely must be paired with ‘to’, and not with a dash.
As a stand-in for ‘and’, implying a connection:
- The Mason–Dixon line dates from the 1760s.
[It was surveyed by Charles Mason and Jeremiah Dixon.] - A difficult father–son relationship often surfaces in Spielberg’s movies.
En-dashes also replace hyphens when preserving the unity of a compound noun:
- Ken is an ex–British Rail driver.
- The New Zealand–born lexicographer Eric Partridge was wary of hyphens.
- Jenna sings in a post–death metal band.
The en-dashes impress on us that Ken isn’t ex-British, Eric wasn’t Zealand-born, and Jenna’s genre wasn’t post-death.
2. Ens (and ems) around clauses
When you want to add tangential information or an explanation to a sentence, but you don’t want to use parentheses (brackets), dashes can be handy. As mentioned, either of the longer dashes can perform this function, so I’m going to fudge this section to cover them both.
There are three punctuation options, all of which are equally acceptable. Number 3 below—closed-up ems—is standard in American English.
1) Spaced ens: The governor – a mechanical device on the engine – limits the RPM.
2) Spaced ems: The symptoms — itching, headaches, rashes — are very annoying.
3) Closed ems: The Britpop bands—Oasis, Blur, Pulp, and so on—were my favourites of the nineties.
When marking off a clause at the end of a sentence, there is just one dash:
- She played it flawlessly – just as we knew she would.
Here, the dash is basically replacing a comma and adding some oomph.
In a similar vein, the dash can denote an abrupt change:
- The adagio was her favourite movement – how could it not be?
- Could you – should you – eat another muffin?
Functioning rather like a colon, it can connect a string of elements to a concluding phrase:
- Porches, glasshouses, conservatories – we can glaze them all.
- Oasis, Blur, Pulp, Elastica, Menswear – these were my favourite Britpop bands.
The em-dash
The em-dash’s name derives from its length, which used to equal the height of the metal type pieces, known as ‘sorts’, in old-school printing technology. When I was a cub editor in the 1980s, our designers still used the point/em/pica measurement system for typesetting. (Gosh, that makes me feel old.) An em-dash is twice the length of an en.
As noted above, the em serves to mark clauses, but there are other uses also.
To mark an interruption:
‘But Bill,’ insisted Ted, ‘why can’t you just—’
‘Just what?’ snapped Bill.
[Some people use an ellipsis here, but the dash is much punchier.]
In place of missing letters (two ems):
- The headstone was barely legible: Here lies C——t Dr——a.
As a ditto in a bibliographic entry (three ems):
Christie, Agatha, N or M? London: Collins Crime Club, 1941.
———, By the Pricking of My Thumbs. London: Collins Crime Club, 1968.