Hyphens and dashes

Hyphens and dashes look similar but are not interchangeable. The hyphen, the smallest of these marks, has three uses in text. First, a hyphen occurs at the end of a line when a word breaks onto the next line. These hyphens are inserted automatically by your word processor.

Second, certain multipart words and names are properly spelled with hyphens (topsy-turvy, cost-effective, Murray Gell-Mann). However, a hyphen is typically not used after a prefix (nonfat, not non-fat).

Third, hyphens are used in phrasal adjectives, such as ten-dollar bill, estate-planning attorney, or clean-air regulations. This is to prevent ambiguities—in the unhyphenated phrase obscene speech restrictions, is obscene an opinion about the speech restrictions, or do the restrictions pertain to obscene speech? If the latter, then you’d write it as obscene-speech restrictions. Nonprofessional writers often omit the hyphens in phrasal adjectives. As a professional writer, you should not.

Dashes come in two sizes—the en dash and the em dash. The em dash () is typically about as wide as a capital M; the en dash () is about half that size. Dashes are often approximated by typing two or three hyphens in a row (---). Don’t do that. Since every typeface has these two dash characters, there’s no reason not to use them.

Mac OS en dash: OPTION + hyphen
Mac OS em dash: SHIFT + OPTION + hyphen

Windows en dash: ALT + 0150
Windows em dash: ALT + 0151

HTML en dash: –
HTML em dash: —

Dashes typically are set flush against the surrounding text, without spaces before and after. But if your em dashes look like they’re being crushed, you can add spaces.

The en dash has two uses. First, it can indicate a range of values, as in 1880–1912, 116 Cal. App. 4th 330–339, or 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). Be careful with citations like Local Rule 7-3. In that case, you want a hyphen and not an en dash, because it’s the multipart name of a single rule, not a range.

Second, the en dash can denote a connection or contrast between pairs of words, for instance conservative–liberal split, Arizona–Nevada reciprocity, or Sarbanes–Oxley Act.

The em dash is a versatile mark used to signal a break between sentence phrases. Use it when a comma is not quite enough, but a colon, semicolon or set of parentheses is a little too much. Em dashes put a nice pause in the text—they are underused in legal writing.