hyphens and dashesUse them, don’t confuse them

Hy­phens and dashes look sim­i­lar, but they’re not interchangeable.

WindowsMacHTML
-hyphen---
en dashalt 0150option + hyphen–
em dashalt 0151option + shift + hyphen—

The hy­phen (-) is the small­est of these marks. It has three uses.

  1. A hy­phen ap­pears at the end of a line when a word breaks onto the next line. These hy­phens are added and re­moved au­to­mat­i­cally by the au­to­matic hy­phen­ation in your word proces­sor or web browser.

  2. Some mul­ti­part words are spelled with a hy­phen (topsy-turvy, cost-ef­fec­tive, bric-a-brac). But a pre­fix is not typ­i­cally fol­lowed with a hy­phen (non­profit, not non-profit).

  3. A hy­phen is used in phrasal ad­jec­tives (lis­tener-sup­ported ra­dio, dog-and-pony show, high-school grades) to en­sure clar­ity. Non­pro­fes­sional writ­ers of­ten omit these hy­phens. As a pro­fes­sional writer, you should not.

    For in­stance, con­sider the un­hy­phen­ated phrase five dol­lar bills. Is five the quan­tity of dol­lar bills, or are the bills each worth five dol­lars? As writ­ten, it sug­gests the for­mer. If you mean the lat­ter, then you’d write five-dol­lar bills.

Dashes come in two sizes—the en dash and the em dash. The em dash () is typ­i­cally about as wide as a cap­i­tal H. The en dash () is about half as wide.

En and em dashes are of­ten ap­prox­i­mated by typ­ing two or three hy­phens in a row (-- or --- ). Don’t do that—it’s an­other type­writer habit. Use real dashes.

The en dash has two uses.

  1. It in­di­cates a range of val­ues (1880–1912, pages 330–39, Ex­hi­bits A–E). If you open with from, pair it with to in­stead of an en dash (from 1880 to 1912, not from 1880–1912).

  2. It de­notes a con­nec­tion or con­trast be­tween pairs of words (con­ser­v­a­tive–lib­eral split, Ari­zona–Nevada reci­proc­ity, Sar­banes–Ox­ley Act).

The em dash is used to make a break be­tween parts of a sen­tence. Use it when a comma is too weak, but a colon, semi­colon, or pair of paren­the­ses is too strong. The em dash puts a nice pause in the text—and it is un­der­used in pro­fes­sional writing.

by the way
  • Don’t use a slash ( / ) where an en dash is correct.

  • Even though the en dash is used for joint au­thors (Sar­banes–Ox­ley Act), use a hy­phen for com­pound names. If the chil­dren of Sar­banes and Ox­ley mar­ried, they’d be known as Mr. & Mrs. Sar­banes-Ox­ley (with a hy­phen), not Mr. & Mrs. Sar­banes–Ox­ley (with an en dash).

  • Em and en dashes are typ­i­cally set flush against the sur­round­ing text. Some fonts in­clude a lit­tle white space around the em dash; some don’t. If your em dashes look like they’re be­ing crushed—par­tic­u­larly if you’re set­ting type on screen—it’s fine to add word spaces be­fore and after.

  • An en dash makes an ac­cept­able mi­nus sign in spread­sheets or math­e­mat­i­cal ex­pres­sions. (See also math sym­bols.)

  • Em and en re­fer to units of ty­po­graphic mea­sure­ment, not to the let­ters M and N. In a tra­di­tional metal font, the em was the ver­ti­cal dis­tance from the top of a piece of type to the bot­tom. The en was half the size of the em. Orig­i­nally, the width of the em and en dashes cor­re­sponded to these units. In to­day’s dig­i­tal fonts, they run narrower.

  • Fans of Robert Bringhurst’s book The El­e­ments of Ty­po­graphic Style (and I am among them—see bib­li­og­ra­phy) may know that he rec­om­mends us­ing en dashes with spaces rather than em dashes. Per­haps this prac­tice is com­mon in Mr. Bringhurst’s na­tive Canada. But in Amer­i­can ty­pog­ra­phy, it’s not.