Em dash (—)

How to read it

Unicode encodes it as U+2014 EM DASH and notes that it “may be used in pairs to offset parenthetical text”. The name comes from printing: the American Heritage Dictionary says it is named for the width of an m, and the AP Stylebook calls it “about the width of a capital letter M”. Matthew Butterick’s Practical Typography puts it differently: em and en are units of type measurement, not the letters, and in today’s digital fonts the dashes run narrower than those units, so an em dash is about as wide as a capital H. It is twice as long as the en dash and longer again than the hyphen.

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Em dash or en dash?

The em dash sets words apart and the en dash joins them. Chicago’s CMOS Shop Talk gives the split: ranges such as 3–5 (“three to five”) take an en dash, and a dash that sets something off from the surrounding text is an em dash. Butterick puts the em dash where “a comma is too weak, but a colon, semicolon, or pair of parentheses is too strong”. The hyphen, shortest of the three, joins the parts of compound words, and Chicago notes it is the only one with its own key on a standard keyboard.

How style guides space it

Style guides disagree about spacing and about which dash to use. Chicago sets the em dash with no space before or after. The AP Stylebook puts a space on either side, except in sports agate, and simply calls it a dash. British publishers more often use a spaced en dash instead: CMOS Shop Talk calls spaced en dashes “more common” in British style, and the Guardian’s style guide says its dashes “should be en dashes rather than em dashes or hyphens”. Butterick notes that the typographer Robert Bringhurst also recommends spaced en dashes, and that in American typography the practice is not common.

When is an em dash used?

In a handful of jobs that style guides list. The US Government Publishing Office’s Style Manual uses it to mark a sudden break or abrupt change in thought, an interruption or unfinished sentence, a replacement for commas or parentheses where that is clearer, and the dash before a credit line or signature. The AP Stylebook names an abrupt change or emphatic pause, and a phrase that contains its own commas. AP sets no limit on how many a story may have, but its guidance warns against “overuse of dashes to set off phrases when commas would suffice”, and the Guardian says a single dash can “add a touch of drama” but should be used sparingly. Longer dashes have their own uses: Chicago keeps the 2-em dash for missing or illegible words and for text that needs to be hidden, the GPO manual uses it when one speaker interrupts another, and both use a 3-em dash in bibliographies for a repeated author.

Do em dashes mean a text was written by AI?

Not according to the AP Stylebook’s editor, Anna Jo Bratton, who wrote in August 2025 that the easy tell “is not the em dash, which has been around for many years”. The idea spread in 2025, when readers began treating the mark as a sign of ChatGPT. TechCrunch reported in November 2025 that it had “popped up everywhere” in school papers, emails and LinkedIn posts, “even if they weren’t a reliable signal of content created by generative AI”, and that OpenAI’s chief executive, Sam Altman, said ChatGPT would now leave em dashes out when a user’s custom instructions ask it to.

Dashes that look alike