Dashes and hyphens look to be similar punctuation marks, but they play different roles. Knowing the difference can add clarity to your meaning.
A dash sets off information that needs emphasis; a hyphen joins words that are used together to form an adjective.
The dash is a detour on the part of the writer, an interruption in midsentence to accent information the writer wants the reader to notice and remember. Many people don’t recall being taught how to use the dash, so they tend to hit the dash key whenever they want to pause. But commas are are for routine pauses; use a dash in these instances:
- To emphasize information that is important: The sentence Be sure to attend the meeting — don’t be late draws the reader’s attention to the urgency of being on time. The dash helps to make it stick. Similar emphasis is delivered in We need solid commitments and detailed proposals — not more empty promises.
- To emphasize unusual information: Cindy received the leadership award — her third consecutive year — at the annual meeting.
- To indicate a sudden break in thought: These efforts – some in place, and others ongoing – are helping employees feel more enthusiastic.
You can use a dash to set off information in the middle of a sentence or at the end.
Hyphens connect two or three words that are serving as one modifier to describe an adjacent noun, as in next-to-last chapter.
When deciding whether to use a hyphen, you have room for discretion. If the reader won’t find the sentence ambiguous, you can omit it. For example, most people won’t hyphenate business writing course, because we are accustomed to seeing those words adjacent to each other. But other situations can cause confusion. On the surface, “he is our new media strategist” means that you have a media strategist who is new to the company. But the writer’s intended meaning was that the strategist had expertise in the field of new media, so it should have been written that He is our new-media strategist. When you do not put in hyphens, new and media each modify strategist individually, so you are saying that he is a media strategist and also that he is a new strategist.
Similarly, toxic gas detector refers to a gas detector that is toxic, which is not the intended meaning. It is a detector that identifies toxic gas, so make it toxic-gas detector.
Caution: Over-hyphenating in your writing creates boring reading, so use judgment and err on the side of clarity. If there is any risk to misreading, insert a hyphen.
One final note: We do not hyphenate words ending in “ly” because no confusion ever seems to result from the word combination in such phrases as freshly prepared food or carefully written proposal.
Ken O’Quinn conducts writing and managerial communication workshops for corporations. A former Associated Press writer, he is the author of Perfect Phrases for Business and is a contributing author of Focus on Them, about leadership.