Em dashes, en dashes and hyphens

For as long as I can remember, I’ve been giving this note to my editing clients: “Replace floating hyphen with proper em dash.” It comes up when I’m proofreading images, like PDFs, and I see a hyphen with just a space on either side connecting two parts of a sentence – like this. But it wasn’t until very recently someone asked me about the term “floating hyphen.” Is that a real thing?

Of course it is, I said. Then I googled it and learned that, apparently, I had made the term up. But my point remains true: A hyphen is not an em dash. Nor is it an en dash. Each of these three punctuation marks has its own special job.

Em dashes, often simply called dashes, are sentence punctuation — a way to connect ideas and phrases and clauses. If you don’t want to use them, you don’t have to. Commas, parentheses and colons can usually get your point across in any spot where you might use a dash.

But if your sentence already has enough commas or if you want to create visual emphasis — like this — you can use em dashes to signal a change in sentence structure or thought. Or you can use em dashes to set off parenthetical thoughts — and who doesn’t love those? — in a sentence. They can also set off lists of items — names, places, things — mid-sentence or at the end. You can even use em dashes for dialogue, datelines or taglines or to show that speech was cut off mid-sentence.

Personally, I consider it a mistake to use an em dash between complete clauses — this sentence is an example. A period or possibly a semicolon would be better. But not everyone agrees with me.

News publications usually put a space on either side of an em dash — making it sort of float. Book and magazine publishing usually omit the spaces—their dashes touch the word on either side. Both are correct. Here's more in my recent column.

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