Think of the em dash as the traditional dash and the en dash as the hyphen.
With our numerous punctuation marks, you would think that one dash is enough, but we have two little marks that are referred to as dashes, and if you are in the publishing business, there are four. So here’s a dash of clarity to help you distinguish the em dash from the en dash.
The em dash is what we have traditionally called the dash. It is thicker and longer than the hyphen, and it is used to separate segments of information, as in this example: When you leave, please turn the lights out–and be sure to lock the door.
A dash is used for three reasons:
- emphasis – When you purposely want to accent information because it’s important and you want it to stick in the reader’s mind.
If you plan to submit a proposal–you only have until Friday —remember to mention the tech support we offer.
- sudden break in thought – I am looking forward to the meeting–I just finished the agenda–because it will be a great chance to hear from everyone.
- unusual information – When she went to a vegan diet, she began working out more and she felt better–her cholesterol dropped 45 points in six months.
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The most common mistake business writers, technical writers, and corporate communicators make with dashes is that they use them interchangeably with commas. Almost anytime they want to pause, they insert a dash. However, a comma is a routine pause, and a dash is not.
Hyphens are shorter and thinner and are used to combine two words that function as one modifier (adjective) to describe something:
- high-speed network
- low-cost loans
- New Hampshire’s first-in-the-nation presidential primary
Don’t over hyphenate, because it makes for boring reading. There is room for judgment. If you think that in a given situation, you could omit the comma without confusing the reader, you can go without it. Here is a hint: read the sentence aloud and if you hear your voice gain speed and squeeze together the two words you are using as one adjective, then it is a signal that a hyphen is appropriate.
Ken O’Quinn is a professional writing coach and former Associated Press writer who conducts corporate workshops on business writing, persuasive writing, and corporate communications writing. He is the author of Perfect Phrases for Business Letters (McGraw-Hill), which is available here at Amazon.com.