Dashed and Confused

Confused about how to use hyphens, dashes (en, em), and minus signs?

I receive lots of manuscripts to review and often see that the author has no clue about when to use a hyphen or a dash (or even that there is a difference). In a few cases, they may realize that the hyphen (-) is too short to use in a place where the en (–) or em (—) dash is required and attempt to recreate it by using two hyphens (--).

There are lots of arcane rules for using these symbols in particular situations, but here's a brief overview that generally holds for most uses.

Hyphen (-): use to join words (e.g., in a compound modifier), with certain prefixes, or to separate syllables of a word (e.g, in a line break). Sea-level rise, how-to book, un-American, science com-
munication. Note that compound phrases require a hyphen only when they precede the noun they modify—not when they follow: "The well-known researcher..." vs. "The researcher is well known."

The hyphen key is located on the keyboard between the 0 and = keys.

Minus sign (−): use to indicate a mathematical operation (subtraction). The minus symbol is longer than a hyphen and similar in length and height to the plus and equals sign symbols.

In word processing programs, you can find the minus sign in the symbol browser.

En dash (–): use to indicate a range of values or in certain word combinations. 5–10 meters, pp. 51–65, Houston–Dallas route, Comet Hale–Bopp.

The en dash is created on a Mac by holding down the option key and pressing the hyphen key. On a PC, you can can create it by holding down the ALT key and typing 0150 on the numeric keyboard. Also found in the symbol library in MS Word.

Em dash (—): use to set off or emphasize a strong break in thought in a sentence. "We all piled into the car—not stopping to worry about our wet clothes—and drove straight back to the city." It's also acceptable to use the en dash in this case, but with spaces: "We all piled into the car – not stopping to worry about our wet clothes – and drove straight back to the city."

The em dash is created on a Mac using shift-option while pressing the hyphen key. On a PC, you can get it by holding down ALT and typing 0151 on a numeric keypad. You can also find it in the symbol library.

For more detailed guidance in the use of dashes and hyphens (and other interesting writing tips), see this post at The Belligerent Copywriters' Guide.