The use of hyphens and dashes in writing can seem an arcane mystery whose secrets are only revealed to grammar pedants. In fact, many people might not even KNOW that there are several different kinds of line that serve several different functions. So, if this is all news to you, read on!
Get In Line!
OK, first things first, let’s get these pesky lines straightened out.
This mark ( – ) is a hyphen or minus sign. It is usually typed by pressing the key next to the “0” on your keyboard.
This ( – ) is an en dash. It is roughly as long as a capital “N” is wide. On Mac computers, you type this by pressing ”alt” + the hyphen key. On Windows computers, you can hold down the “alt” key and type “0150” on the keypad. However, Microsoft Word also changes hyphens to en dashes automatically when you put two spaces on either side (i.e. word-space-hyphen-space-word).
This ( — ) is an em dash, so called because it is roughly as long as a capital “M” is wide. On Mac computers, you can type this by pressing “alt” + shift + hyphen. On Windows, you can hold down the “alt” key and type “0151” on the keypad. Alternatively, Microsoft Word automatically formats a double hyphen as an em dash when typed between two words (i.e., word-hyphen-hyphen-word).
When to Use Dashes and Hyphens
So what are they all for? Let’s start with the hyphen. Its use is widely disagreed on, so we’ll stick a few generalizations. Use it for:
Joining words to make a compound noun (e.g., “merry-go-round”)
Forming a compound adjective (e.g., “self-employed”)
Double numbers (e.g., “twenty-seven”)
Some prefixes, especially to prevent a letter collision (e.g., we write “anti-inflammatory,” not “antiinflammatory,” because of the double “i”)
For more information on the hyphen, take a look here.
Dashes come in two kinds: en dashes (–) and em dashes (—), with their names based on their differing lengths. The main use of em dashes is to set part of a sentence apart from surrounding text:
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The Etruscans—a largely mysterious civilization—left behind few archaeological artifacts.
Typically, em dashes are unspaced when used parenthetically.
The main use of a en dash is to indicate a range of values or a sequence of some kind (e.g. ’24–50 degrees’ or ‘London–Paris’). You can also use an en dash to indicate a connection (e.g. ‘Anglo–American relations’).
In addition, en dashes can be used parenthetically, like the em dashes above. This is more common in the UK than the US, and you would usually add spaces before and after parenthetical en dashes:
The Etruscans – a largely mysterious civilization – left behind few archaeological artifacts.
Whether to use em dashes or en dashes to set apart part of a sentence is largely a matter of preference. However, if you’re using a style guide, make sure to check for guidelines on dash usage. And whichever style of dash you decide to use, make sure to apply it consistently.
We hope that underlines the differences, and that now you’ll cut a dashing figure when you hand in all your correctly punctuated papers! [Groan…]