Today’s topic is dashes: when to use them and when not to use them. At the risk of boring you—although you are reading a post about dashes so you reallyhave only yourself to blame—I am going to start withthe distinction between hyphens and dashes.Ahyphen joins two words intoa unit (e.g., ‘on-site manager’ or ‘lotus-eater’) or indicates a word break at the end of a line of text. A short dash (often called an en-dash because it isthe width of the letter ‘n’) separates items such as dates or page numbers (e.g., 1711–1776 or pp. 106–7). Along dash (often called an em-dash because it is the width of a letter ‘m’) is what we will be talking about below. A hyphen isproduced byasimple keystroke on your keyboard; dashes are symbols that can be inserted into a document in a variety of ways. For more on hyphens and dashes, you can consultthe online Chicago Manual ofStyle.
Just in case anyone is still reading, I am now going to talk about using dashes in your writing. First,we will look at single dashes, which I will argueare insufficiently formal for academic writing, although some would disagree. Here is an example:
Recombinant DNA technology has left an indelible mark on the basic ingredient of human survival—food production.
This dash could be replaced by either a comma or a colon. I would suggest a colon because a colon signals unambiguously that what follows will complement or complete what precedes it. A comma would work, but since commas play so many roles in our writing, Igenerally choose a colon over a comma when theygo head-to-head. Here is another example:
The range of Hume’s writingshelp us to understand his reservations about a revolutionary approach—such an approachwould be unlikelyfor a thinker so immersed in historical considerations.
In this case, you could replace the dash with either a semicolon or a period. Generally, a semicolon will work best since it will provide the closeness that the author was trying to convey with the dash.
I am only arguingagainst the single dash in academic writing—it isabsolutely fine in a more casual contextlike, say, ablog post. My reason forthis advice is that the dash can play the role of a comma, colon, or period without doing anything unique. Nothing special is addedand something may be lost. You may lose clarity, and you will certainly lose formality.I am being, of course, overly opinionated; if you wish to defend the use of single dashes in formal writing, I hope you’ll do so in the comments below. One possible line of defence is certainly the drama of the single dash; since it breaks up a sentence in an unconventional manner, it does draw real attention to what follows it. Now let’s turn to the use of double dashes.
Double dashes are used instead of commas (orparentheses) to interrupt a sentence. The phrase separated by dashes must be grammatically inessential, by which I simply mean that the sentence will still work without that phrase. Here is anexample:
The issues that confront students entering late-stream French immersion programs—most importantly, their lack of familiarity with instructional vocabularies—are a pressing concern for school administrators.
It is often said that we use dashes to signal that something crucial is being added to a sentence anduse parentheses to signal that the interruption is relatively unimportant (e.g., to give dates or citations or examples).In this schema, commasfall somewhere in the middle. There is some truth to this division, but I find the nextthree principles more helpful in deciding whether to use double dashes:
1.Most importantly, double dashes can be usedtoaddan element to a sentence that already hasits share of commas.
2. Double dashes are very common in some fields (most humanities fields, for instance) and rare in others (in many scientific fields, for instance). If they are rare in your field, it is unlikely that you would want to use them.
3. Regardless of field,double dashes are a stylistic variant and should be used sparingly; they draw attention to themselves, and the audience will grow tired of them if they are overused.
Overall, I suggest using double dashes—if they are appropriate to your field of study—in moderation and replacing single dashes with colons, commas, or even periods, if only in your formal writing.
Note: For more on dashes, see Interrupting Yourself.
