One thing I often notice in student papers is the random use of dashes and hyphens. In most cases, people simply use hyphens only, probably because they are easiest to find on computer and smartphone keyboards. Another reason is that only very few seem to be able to tell the difference between -, –, and —.
Aren’t they all the same, anyway? A dash is a dash is a dash. Actually, not at all—each of these has a specific function. These marks are not interchangeable. Let’s see which one is which and when to use them.
A hyphen is a punctuation mark used to connect certain words, such as compound nouns and numbers. A hyphen is shorter than the dashes:
ninety-three; short-term; part-time; high-tech, low-cost.
The rules of hyphenating words in English are a bit inconsistent and I won’t go into them in this post. You can consult the following Purdue University web page which provides a concise overview.
‘En dash’ is called like that because its length is the same as that of the capital letter N. This is the mark you would use to represent words like ‘to’ and ‘through’ when writing page numbers, times and dates, also directions and sports results.
For homework, please do the exercises on pages 23–25. [to / through]
She has a part-time job, working 20–30 hours a week. [to]
The London–Belgrade flight takes about 2.5 hours. [to]
Our team was beaten 4–1. [to]
None of these are compound nouns, so it would be wrong to use hyphens in such instances.
‘Em dash’ is the longest. You’ve guessed it: its length is the same as that of the capital letter M. It’s also the most versatile.
It serves to indicate a pause in a sentence, which can be used to add extra information. Depending on context, it can replace a comma (,) semicolon (;) or colon (:), and sometimes you can use parentheses (brackets) instead of em dashes. With an em dash, though, the added piece of information is usually more emphatic than it would have been with those other punctuation marks. The use of em dash is thus a kind of stylistic device, used by writers to hint at the nuances of meaning within a sentence, such as hesitation or surprise. Or it can be used to provide additional examples of something, especially when followed by words like ‘namely’, ‘that is’, ‘for example’.
Traditionally, there are no spaces between an em dash and the words coming immediately before and after it, although that seems to be changing nowadays, especially in the press. Some writers and publishers actually prefer the spaces, so there are no strict rules regarding this any longer.
Mark was a good friend of mine—the very best friend one could wish for.
You could easily tell—namely from his facial expression—that he was very unhappy.
She gave a lot of excuses—all of them lies—as to why she was always late for work.
From these examples you can see that the use of em dash is totally different from that of hyphens and en dashes. If you want to see more detailed explanations for the specific uses of these three punctuation marks, I can recommend the article A Guide to Em Dashes, En Dashes, and Hyphens found on the Merriam-Webster website.
If you can’t find the en dash and em dash on your computer keyboard, you will definitely find them under Special Characters in your word processor. If you happen to be using Google Docs, click on Insert > Special characters and then type in the search box the punctuation mark you are looking for (simply typing ‘en’ or ‘em’ will suffice) and it will show in the box to the left, as seen in the snapshot below. In some word processors, you can also type two hyphens (with no space in between) and they will automatically convert into an em dash.
I hope this brief guide was helpful. If you want to practice this a bit, write a few example sentences and post them in the comments section below.