May 15, 2014

Weekly Language Usage Tips: Dashes and hyphens

Posted in dashes, hyphen at 9:29 am by dlseltzer

I have several questions from readers that I was going to start to answer today, but I changed my mind. (Don’t worry, I will get to them all.) I’ve been reading several manuscripts lately, and I discovered that there was a real need for me to do another review of dashes (m and n) and hyphens and how to use them, so I am putting aside the questions to quickly review this.

This is an m dash: —. It is so named because it is the size of the letter m. It is used to show emphasis and to separate one part of a sentence from another:

This scientific discovery—the first to show the relationship between obesity and physical health outcomes—was presented at an international meeting of researchers.

You can use the m dash in pairs as above or as a single dash:

We found that the costs were highest for cohort A—despite their demographics being the same as those of cohort B.

As you can see, there is no space on either side of the m dash. Newspapers and those who follow AP style use spaces, but we don’t. AMA and Chicago style guides eschew the spaces, and we should, too.

This is an n dash: –. As you can probably guess, it is named for its width, which is equal to that of the letter n. The n dash is used far less frequently than the m dash or the hyphen and is generally used to show a range.

The trial ran from January–March.

The subjects were between 18–25 years of age.

Again, there are no spaces on either side of the n dash. Go that? No spaces.

Both dashes can be found in Word, under Insert, Symbol, Advanced Symbols. I found that making keyboard shortcuts for these symbols is very handy and makes it easier to insert them without bothering with menus.

And at last, there is the hyphen: -, which isn’t a symbol at all, but a bit of punctuation. The hyphen has several uses, including: the expression of compound words or compound adjectives, a separator used with prefixes such as ex and semi, and a means of ensuring clarity.

The able-bodied firefighters are working tirelessly in California.

This semi-soft cheese is going to make the salad sublime.

I need you to re-sign this letter.

Again, no spaces around the hyphen.

I have a theory about why there is confusion about putting a space around dashes. First, we see it that way in newspapers, and that doesn’t help. But second, we sometimes use the hyphen to represent the m and n dashes.

If you don’t use the m dash, you can represent it by using two hyphens side by side.

 She is studying modeling- -she wants to teach computational modeling when she graduates.

And if you don’t use the n dash—and this is where the confusion comes in—you can represent it by typing a hyphen, surrounded by spaces.

The participants in the control group were aged 18 – 40.

Just a theory, but I suspect it has something to do with why we perceive a need to surround our dashes with spaces. But the bottom line is: DON’T—they just aren’t needed.



  1. Brian Hahn said,

    Quick tip. MS Word already comes with shortcuts for n- and m-dashes.

    n-dash: Ctrl + –
    m-dash: Ctrl + Alt + –

    • Brian Hahn said,

      Oh, the hyphen is the one on the numpad, not the one next to 0.

      • dlseltzer said,

        Actually, it depends on the computer and keyboard–I am using a Macbook Air which has no numpad, and the hyphen is, indeed, next to the O.

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