In the family of punctuation marks, there are three horizontal strokes, each with a very different function. In ascending order of length, they are the hyphen, the en dash and the em dash; and they look like this: ‘-’, ‘–’, and ‘—’.
The shortest of the three, the hyphen, links two or more words together to make a single unit of meaning, usually a compound adjective:
- My five-year-old child has just started school.
- You will enjoy this television’s cutting-edge features.
Please note, however, that if they are not being used as a compound adjective the words should not be hyphenated.
- My child is five years old.
- The television is at the cutting edge of technology.
The en dash, so called because it is the same width as a printed lower-case ‘n’, is used to join two equal components where there is a logical connection or opposition:
- Did you watch the Barcelona–Juventus match?
- I am taking the Glasgow–London express tomorrow morning
- Susanna West, CEO 2008–2016.
In these examples, the first ‘en’-dash serves as an alternative for ‘versus’ or ‘against’. In the next two sentences, it replaces the word ‘to’. Please note, however, that the word ‘to’ should be used if it is paired with ‘from’: ‘She was CEO from 2008 to 2016′; ‘the train from Glasgow to London’.
The em dash, as its name implies, is the width of a printed lower-case ‘m’, and double the length of an en dash. It is used singly to replace an introductory punctuation mark such as a colon, or in pairs as a form of parenthesis:
- Corfu is the most beautiful of the islands — green, serene, and relaxed.
- Just then — and it really was unexpected — there came the hoot of an owl.
So next time you want to just throw up your hands and exclaim ‘Oh, dash it all!’, just be careful which one you mean…