Terrible news. Apple is replacing the long-running convention of typing two hyphens to obtain an em dash or “long dash.” That is, if you type --, many places in the interface in which autocorrection is enabled or third-party software takes advantage of autocorrection, it’s turned into —.
Instead, two hyphens become the shorter en dash, or –, which you may never have heard of if you’re not a print or Web designer or otherwise interested in the intricacies of formatting things. To get an em dash, you will have to type ---, a convention that also appears in TeX, a mathematical formatting language developed by Donald Knuth.
iOS 11 “smart punctuation” converts dash-dash to an en-dash (–). Am I the only one annoyed by this? I think it should be an em-dash (—).— John Gruber (@gruber) July 6, 2017
Update: In the release version, Apple contextually replaces -- with — (em dash) to connect words when you type with or without spaces on either side. If you type a number and two hyphens, it turns into a – (en dash).
Why is this terrible news? Some have argued with me on Twitter that it’s more logical: - for hyphen, -- for the longer en dash, and --- for the longest em dash. You type more hyphens to get a longer dash.
My rejoinder is twofold. First, most people rarely use an en dash, although I’d like to increase that number. Second, a billion people have learned that typing -- leads to a long dash. I may be exaggerating the number, but given that Microsoft Word,* Pages, and other desktop software performs this substitution silently, it’s a widespread convention being overturned.
I’d therefore argue this is inefficient, confusing, and inconsistent. If one wants an em dash, one is now forced to type or tap three characters rather than two. It’s confusing, because typing two hyphens will no longer produce the expected result for those paying attention. It’s inconsistent, because it’s unlikely that nearly every other piece of software in use other than TeX that offers an autocorrection for -- will change its behavior to match Apple’s.
The long dash also has a particular visual identity that provides the eye with a cue to take a long mental pause, one that's not nearly long enough with the en dash.
If you're not familiar with the difference among these dashes, the simple explanation for standard American usage is:
- A hyphen, -, separates words in phrases, as in “least-used product” and is used for line breaks in books and other matter. (There’s an exception for some compounds; see below.)
- An em dash, —, is used to set off a phrase—one in the middle of the sentence—that’s not quite a parenthetical, but it isn’t so germane as to be set off by commas. It’s also used as a sort of pause to emphasize something—something important at the end of a sentence.
- An en dash, –, separates ranges for dates, numbers, and quantities—like 9–5 and January–August. It’s also used for certain kinds of connections, directions, and contrasts, such as standing in for “versus” in Lincoln–Douglas debates or in place name pairing like Alsace–Lorraine, where both are separate places being referred to together. (You can read a more elaborate explanation here.)
The inestimable Butterick’s Practical Typography, which you should memorize, has more typographic detail. On a Mac, type an en dash as Option-hyphen and an em dash as Option-Shift-hyphen. In iOS, long press the hyphen and pick the option to its right for an en dash and to the right of that lies the em dash.
This change appears in the beta release of iOS 11, so it may not wind up in the final version later this year.
A few miscellaneous em notes
What makes this more confusing is that in Australia, Canada, and the United Kingdom, typographic conventions shifted, and an en dash with a full word space on either side is frequently used instead of an em dash! Thus our English-speaking cousins have no complaint. My * above references that Word turns [any character]--[any character] into —, but if you type [space]--[space], Word follows the non-U.S. format and changes the hyphens to an en dash.
An em was traditionally the width of the height of a font, forming a square metal piece, which roughly corresponded to the letter M in that font, and is a standard unit of typographic measurement. An em dash eventually became as wide as a H rather than an M. An en was once exactly half an em. Spacing in metal type was measured as X to an em, like “3 to an em,” or as X-em spaces, meaning three of those spaces added up to the same width as an em.
An em dash often has a hair space (anything less than 5 to an em) or slightly larger on either space to set it off from text. A manual from 1887 notes, “In using an em dash, a hair space should always be placed on each side of it in book work, which gives it a neat and clean appearance in print.” It may be set these days with no spacing at all or a full word space, neither of which looks right to me in print, but works better online.
The Atlantic ran a story in 2016 that misidentified the en space. The writer mistook the en space (2 to an em) for any word space. The proper word space in metal-type days was 3 to an em for normal text.
Typesetters in the olden days were paid "by the em," meaning they were paid a fee for how much they set in a given font, no matter the size, which caused all sorts of complications.
In older usage, three em dashes in a row indicated a redaction, like omitting someone’s name in the press. This survives as a Unicode character (⸻)! (Unfortunately, not every font has the glyph, so you may not see it in the next paragraph.)
In a sentence, it might appear as, “Mr M⸻ of Green Bay told Miss B⸻ of Bowling Green that the check was in the mail.” I found a wonderful example from 1852 of someone speaking aloud the term “three em dashes” either due to a typesetting error (a direction to the compositor to use three em dashes was misunderstood) or as a verbalization of punctuation.
Typewriting and typesetting have distinctly different paths and purposes, though practical machine typesetting and practical typewriters became possible at around 1880. Typewriting manuals told typists how to prepare business correspondence, but also how to type copy intended to be typeset and copy that emulated typesetting. Two hyphens for a long dash dates back to at least the 1890s.