How to Use a Dash

The punctuation mark sets off parenthetical elements

How to use a dash

 ThoughtCo

The dash (—) is a mark of punctuation used to set off a word or phrase after an independent clause or a parenthetical remark (words, phrases, or clauses that interrupt a sentence). Don't confuse the dash (—) with the hyphen (-): the dash is longer. As William Strunk Jr. and E.B. White explained in "The Elements of Style":

"A dash is a mark of separation stronger than a ​comma, less formal than a colon, and more relaxed than ​parentheses."

There are actually two types of dashes, each with different uses: the em dash—also called the "long dash," according to Oxford Online Dictionaries—and the en dash, which doesn't have another name but falls between the hyphen and em dash in terms of length. The en dash is so named because it is approximately the equivalent width of the uppercase letter N and the em dash is roughly the width of an uppercase M.

Origins

Merriam-Webster says the word dash comes from the Middle English word dasshen, which probably derives from the Middle French term dachier, meaning "to impel forward." One current definition of the word dash is "to break," which would well describe what a dash does in syntax.

The online Online Etymology Dictionary says the dash—a "horizontal line used as a punctuation mark"—first appeared in writing and printing in the 1550s. By the late 1800s, the dash had taken on some very specific roles.

According to Thomas MacKellar, in his 1885 book, "The American Printer: A Manual of Typography" :

"The em dash...is frequently used in particular works as a substitute for the comma or for the colon, and is found particularly serviceable in rhapsodical writing, where interrupted sentences frequently occur."

 MacKellar noted several specific uses for the dash, including:

  • A sign of repetition in catalogs of goods, where it means ditto
  • In catalogs of books, where it was used instead of repeating an author's name
  • As a stand-in for the words to and till, as in chap. xvi. 13-17

The last use would today be an en dash, which indicates a range.

The En Dash

Though the Associated Press does not use the en dash, the press service nicely describes how other styles do use the shorter dash. Some other styles call for en dashes to indicate ranges of dates, times, or page numbers, or with some compound modifiers. For example:

  • He worked from 9–5. 
  • She works from 8 a.m.–5 p.m.
  • The festival will take place March 15–31.
  • For your homework, read pages 49–64.

To create an en dash using a keyboard on a Windows-based system, hold down the Alt key and simultaneously type 0150. To create this punctuation mark on a Macintosh-based system hold down the Option key and press the Minus key [-]. American Psychological Association notes that you would use the en dash for:

  • Items of equal weight (test–retest, male–female, the Chicago–London flight)
  • Page ranges (in references, “...Journal of Applied Psychology86, 718–729”)
  • Other types of ranges (16–30 kHz)

    Angela Gibson, writing for the MLA Style Center, a writing resource for the Modern Languages Association, says the organization uses an en dash when a single compound adjective is a proper noun, as in:

    • Pre–Industrial Revolution city

    She notes that the MLA also calls for an en dash when a compound in the predicate position includes a proper noun:

    • The crowd was Beyoncé Knowles–obsessed.

    The Em Dash

    The AP, which does use em dashes, explains that these punctuation marks are used:

    • To signal an abrupt change
    • To set off a series within a phrase
    • Before attribution to an author or composer in some formats
    • After datelines
    • To start lists

    AP style calls for a space on both sides of an em dash, but most other styles, including MLA and APA, omit the spaces. On a Windows-based system, you can form an em dash on a keyboard by holding down the Alt key and typing ​0151.

    To create the em dash on a Macintosh-based system, hold down the Shift and Option keys and press the Minus key [-], notes Techwalla, adding that alternatively, you can press the Hyphen key twice and press Space.

    There are two basic ways to use an em dash in a sentence:

    After an independent clause: Author Saul Below, in "My Paris," provides an example of using an em dash after an independent clause:

    "Life, said Samuel Butler, is like giving a concert on the violin while learning to play the instrument—that, friends, is real wisdom."

    To set off words and phrases: Writers have effectively used em dashes to shoehorn a parenthetical thought or remark into a sentence, as this quote illustrates:

    "Copper Lincoln cents—pale zinc-coated steel for a year in the war—figure in my earliest impressions of money."

    —John Updike, "A Sense of Change," The New Yorker, April 26, 1999

    Thoughts on the Dash

    For a tiny punctuation mark, the dash has sparked an unusual level of debate among writers, grammarians, and punctuation experts. "The dash is seductive," says Ernest Gowers in "The Complete Plain Words," a style, grammar, and punctuation reference guide. "It tempts the writer to use it as a punctuation-maid-of-all-work that saves him the trouble of choosing the right stop." Some have expressed support for the dash:

    "The dash is less formal than the semicolon, which makes it more attractive; it enhances conversational tone; and...it is capable of quite subtle effects. The main reason people use it, however, is that they know you can't use it wrongly."

    —Lynne Truss, "Eats, Shoots & Leaves"

    Other writers strenuously oppose using the mark:

    "The problem with the dash—as you may have noticed!—is that it discourages truly efficient writing. It also—and this might be its worst sin—disrupts the flow of a sentence. Don't you find it annoying—and you can tell me if you do, I won't be hurt—when a writer inserts a thought into the midst of another one that's not yet complete?"

    —Norene Malone, "The Case—Please Hear Me Out—Against the Em Dash." Slate, May 24, 2011

    So, next time you look in your toolkit of punctuation marks and see the en dash or em dash just waiting to be put to work, ensure that you are using these marks for the right reasons and following the rules discussed. Ask yourself if your parenthetical remark will add nuance and insight to your writing or just confuse the reader. If it's the latter, return the dashes to your punctuation tool bag and use a comma, colon, or semicolon instead, or revise the sentence so that you can omit the dreaded dash.