The en dash

Longer than a hyphen, about half the width of an em dash, the en dash (–) was historically related to the width of the lowercase “n” in typeface.

The en dash is commonly employed for the following:

• Number ranges, in the sense of “to.” 
  • e.g., 11:00a.m.–3:00pm; 1995–2004; New York–Chicago flight; Bengals lost to the Giants 21–10; Genesis 1:12–15; (Smith, pp. 82–105); 300–350. And after a date to indicate a continuation, such as Smith (1952–).
• Certain compound adjectives
  • e.g., replacing a hyphen when some elements are already an established compound (hyphenated or otherwise): Coca-Cola–obsessed drinker; New York–based writer; post–World War I author.
• Sometimes in place of hyphens to separate numbers that are not ranges
  • e.g., sometimes used for telephone numbers. But this also is where the “figure dash” comes in: as wide as a standard numeral, it is used as the separator in phone numbers, such as 323‒555‒6349.

Typing an en dash is not as easy as typing a hyphen, for the latter symbol appears on a keyboard, the former is nowhere to be found. On a PC, one can use the “insert symbol” function to find the en dash (and other dashes) or hold down the ALT key and type 0150 on the numerical pad of the keyboard. On a Mac, one can hold down the Option key and type the minus sign. Microsoft Word also allows an option (you need to make sure Auto Format is set up accordingly) to replace two hyphens between words with either an en dash (if a space on either side) or an em dash (if no space).

The convention in adding en dashes is that there is no space between the dash and the words/numbers on either side of the dash.

Note that while a hyphen typically connects two things that are very closely related (such as compound adjectives and compound names), the en dash commonly connects things related by distance, such as range in years (1995–2004) or months (June–September) or pages (pp. 82–105) or actual distances (Boston–New York train). 

The em dash

The em dash (—) is the versatile punctuation mark that one normally thinks of when hearing the term dash. Historically, it was related to the width of the upper-case M.

The em dash is especially common in indicating a strong break in the structure of a sentence, such as with the Twain quote at the top of this article. The dash can be useful in breaking up a long and complex sentence or in creating a dramatic interruption in the flow or rhythm of the sentence. The em dash can replace a semicolon, colon, parenthesis, and comma.

The following are some applications of this archtypal dash:

• Indicating an abrupt break in thought or sentence structure
  • e.g., see the Twain quote above
• Indicate an interruption in dialogue.
  • e.g., “What must I do to impress—,” William began before his wife cut him off. “Impress who?” his wife demanded. Or “Can she—will she—do what I ask?” inquired Frank. [But not to be used to signify stuttering or otherwise faltering in speech. In those cases, the ellipsis should be used (such as “The c…c…car uh, oh, st…st…stopped.”)
• Separating a subject or series of nouns from a pronoun that introduces the main clause.
  • e.g., Partying, gambling, drinking—he tried each and found them unsatisfying.
  • e.g., Workaholic—that was a term he grew to dislike.
• In place of commas or parenthesis (enhancing readability, adding emphasis)
  • e.g., When he finally arrived—six months after he said he would—everyone was eager to hear his story.
  • e.g., Please remind my secretary—Ann Smith—to set up the meeting.
  • e.g., Bill took his computer—a small, black, laptop—to the meeting.
  • e.g., It took two weeks to travel by train from New York to Georgia—this is 1800 we are talking about—and he hadn’t been looking forward to such a long journey.
  • The em dash can improve readability when it replaces a comma that would normally be used to offset an appositive if the appositive has several commas. For example: There were six people—Frank, Emily, Sharon, William, Rick, and Sam—waiting in the board room. Or: The one H and five W words—who, what, when, where, why, and how—need to be addressed on every project.
• For replacing a colon or semicolon  (perhaps to add dramatic emphasis)
  • Hugh worked hard every day—his wife played hard every day.
  • Remember to do three things—rest, rest, and rest.
• Mark an author’s name after a quotation
  • “Hard work beats talent when talent hardly works.”  – Anonymous.
• In French (sometimes British), occasional use in place of quotation marks to set off dialogue
  • — Why do you think he said that?
  • — Because he could.

While the em dash is a very versatile punctuation mark, its overuse in a paragraph can disrupt the flow to the point of being annoying to the reader. The Chicago Manual of Style also notes that a sentence should never have more than two em dashes.

When it comes to spaces before or after a dash, there are two different conventions. The Chicago Manual of Style states one should not use a space, as in all the examples above. But some styles, notably AP, put spaces at both ends of the dash.

As far as other punctuation, a question mark or exclamation mark may precede an em dah, but, according to The Chicago Manual of Style, never a colon, semicolon, or comma and only rarely a period.

In American English, one may use two consecutive hyphens to represent an em dash; in British English, the convention is to use a single hyphen separated by spaces.

2-em dash

Twice the size of an em dash, the 2-em dash (——) represents a missing word or part of a word, such as blanking out a name or something illegible or an expletive. The Chicago Manual of Style recommends using a space on both sides of the 2-em dash when it replaces a whole word, no space when part of a word. An example of both a missing word and part of a word would be: Oh, — it. Why does Z— do this to me all the time?

It may be hard to find a 2-em dash in your word processing program, but you can simply string two em dashes together.

3-em dash

The 3-em dash (———) is handy for citations; it is used to indicate previously named, and immediately preceding, authors without repeating the names.

An example would be; 

Straws, Richard.  2017. Hugh Holiday. Gouldsboro, PA: Hudson MacArthur Publishers.

———.  2017. Running with the Curimbatá. Gouldsboro, PA: Hudson MacArthur Publishers.

———.  2019. Future Jaú. Gouldsboro, PA: Hudson MacArthur Publishers.