Well you learn something new every day don’t you? Until today, I’ve freely interchanged hyphens, en and em-dashes on a whim, without really giving any thought or consideration to the fact that there might be grammatical rules attached to their use — which, of course, there are. Fortunately they are simple rules too.

There are four different dashes that appear to be interchangeable but are, in fact, quite distinct.

Hyphen

The hyphen (-, -) is used to join related words. For example: run-of-the-mill. It is also used to split words over a line break. The hyphen is the shortest dash of the four.

En-dash

The en-dash (–, -, –) is used to indicate a range. For example: the play runs from the 10th – 16th July. The en-dash can correctly be used with or without enclosing spaces. The en-dash is between the hyphen and the em-dash in length.

Minus

The minus (−, −, −) is used in mathematical equations to indicate subtraction. For example: 10−6=4. The minus is slightly longer than the en-dash.

Em-dash

The em-dash (—, — —) is used to indicate a break in thought in written text. For example: the aircraft took off — the noise from its engines rattling nearby windows. It is also used to encapsulate a distinct thought within a sentence, in which case the thought should have an em-dash as a both a prefix and suffix. For example: Harrison stopped to read the manual — something she would never usually do — before she turned to the complex control panel. The em-dash is the longest dash of the four.

Easy! I’ll take care to use these correctly from now on.