Em dashes are handy little items for setting phrases apart for special attention, but be cautious when employing them, because when misused, they can obscure rather than assist in comprehension:
1. “For the most part, this water comes from aquifers — that’s groundwater — or from surface waters — that is, rivers and lakes.”
When em dashes come in pairs, what lies between is a parenthetical digression that merits a more dramatic break than that indicated by a brace of commas or two parentheses. If the parenthetical phrase ends the sentence, however, only a single em dash is needed. But three or more em dashes in one sentence creates an ambivalence in the sentence structure.
In this case, it’s better to use parentheses — and to avoid mixing em dashes and parentheses for digressions of equal or parallel impact, use them for the second digression as well: “For the most part, this water comes from aquifers (that’s groundwater) or from surface waters (that is, rivers and lakes).”
2. “Her recent roles have shown her interest — and her ability — to go beyond the usual popular movie.”
Be careful that when a phrase is parenthesized, what precedes and follows it is grammatically sound: “Her recent roles have shown her interest in going — and her ability to go — beyond the usual popular movie.”
3. “The collapses could play out in the seven states that rely on the Colorado River and its tributaries — Arizona, California, Colorado, Nevada, New Mexico, Utah, and Wyoming — as ever-increasing water use, ever-growing population and a changing climate shrink the flow.”
If the parenthetical delineates a list or the parts of a whole, as here, the opening em dash should immediate follow the whole: “The collapses could play out in the seven states — Arizona, California, Colorado, Nevada, New Mexico, Utah, and Wyoming– that rely on the Colorado River and its tributaries as ever-increasing water use, ever-growing population and a changing climate shrink the flow.” (Otherwise, the sentence identifies the states as tributaries.)
4. “There may be a decrease in prices—but incomes are rising—so that outcome may not happen.”
When you use an em dash, you should know what you’re getting yourself into. In this sentence, the writer meant to set off the entire second clause, not just the parenthetical, which is bereft without the phrase following the second em dash: “There may be a decrease in prices—but incomes are rising, so that outcome may not happen.”
5. “Maybe it’s just because no matter how many people have been through here — the space remains the same, seemingly untouched by human hands.”
By the same token, many sentences simply don’t merit even a single em dash — there’s nothing to mark off for emphasis. Perhaps the writer meant to place the em dash in lieu of the comma after same, rather than the one following here, but commas suffice in both positions: “Maybe it’s just because no matter how many people have been through here, the space remains the same, seemingly untouched by human hands.”
Great article! I read the first couple chapters a very popular book (I won’t mention the name here), and the author used a significant amount of ’em dashes.’ I counted 50 of them in one chapter! I’m surprised the editor didn’t mention it to the author.
An orthographic question: When using an em dash, should it butt up against the words on either side of it, or should it be cushioned with a space on either side? I see that you did it both ways in your column. There seems to be no standard. Although it’s not a big deal, I wonder if there’s a printer’s convention about this. I used to put in the cushions, but now I’ve stopped. Do I have bigger issues to worry about? Yep! Thanks for the wonderful newsletter.
I adore em-dashes, when they are used properly, and this is a good post because you do point out occasions when they should not be used.
The only part that annoys me is the first example. Something about the word “that’s” makes it seem as if the writer feels s/he is talking to an idiot. As if saying, “that’s groundwater, in case you idiots didn’t know that.” This is not the first time I’ve come across this sort of construction when the writer is trying to explain something. I think a better sentence construction would be “This water comes from aquifers, meaning groundwater, or surface waters, meaning rivers and lakes.” Another option, altho a bit more cluttered, would be to use parentheses, as in “This water comes from aquifers (groundwater) or from surface waters (rivers and lakes).”
“The Professor and the Madman” has too many em dashes; still, a great book.
Em-dashes should be separated from the surrounding text by a hairline space (though some fonts have the space built in to the dash; it’s a pain when you want to put three dashes together, in a bibliography entry, etc., though, because then you don’t want space between them!). When you don’t hairspaces (in text, word-processors, etc.), don’t space them at all. You can also use an en-dash with spaces in place of an em-dash. People use spaces on internet forums to allow line breaks around the dash.
BTW, Rebecca: it’s couple of chapters, and significant number of em dashes (“couple chapters” is just bad English, and “amount of dashes” makes it sound like you can fractions of a dash).
I adore em-dashes! I love seeing them in a book I’m reading. I often wonder if the lack of em-dashes in books is an indication that the author is uncertain of how to use them. Of course, they could simply prefer other punctuation.
It’s so embarrassing when you pontificate authoritatively and are wrong. The corrected sentence in Example 3 above says “Wyoming-hyphen” when it should say “Wyoming space em-dash”. I’m sure this is just a typo or artifact of html, but it is incorrect nevertheless.