Hyphens, En Dashes, and Em Dashes—Oh My!

One of the least-understood sets of punctuation in writing are dashes. Most people don't realize there are three distinct versions of them, and they are used for very different purposes.

The most commonly used and confused dash is actually not a dash at all but just the plain old hyphen (-), which is the same character used for a minus sign. You will see this used sometimes in books where a word is split across a line. This is something for book designers to worry about, though, not writers. You should never split a word across a line yourself as a writer. The hyphen is also used to hyphenate two words, as in "twenty-one" or in compound modifiers, like "a little-known restaurant." There are rules governing when a compound modifier should be hyphenated, and they can get pretty confusing. Here's a quick guide for you:

• Don't hyphenate compound modifiers that come after the words they modify (e.g., "a restaurant that is little known").
• Don't hyphenate compound modifiers if one of the words in an adverb (e.g., "a rapidly filling cup").
• Spelled-out numbers between one and one hundred should always be hyphenated (e.g., twenty-one, ninety-nine).
• Compound modifiers before words should usually be hyphenated (e.g., "a three-year-old boy" or "an American-football player"). The second example demonstrates why hyphenation is needed for compound modifiers. If the word wasn't hyphenated, the phrase could be interpreted either as a player of the American version of football or as a player of football who is American.

The second form of dashes is the en dash, so named because it is roughly as long as the lowercase letter n. It's bigger than a hyphen but smaller than the em dash. This dash is used between ranges of numbers or values, as in "Arkansas beat Ohio State 31–3 in the Sugar Bowl." (And yes, that is wishful thinking!) En dashes are also used in the rare event of a compound modifier where one or both of the modifiers is made up of two words, as in "a pre–Civil War house." You can create an en dash in Microsoft Word by pressing ctrl+the hyphen on the number pad.

The em dash is the most utilitarian of the dashes and was so named because it's roughly the size of a capital letter M. To create an em dash in Microsoft Word, press ctrl+alt+the hyphen on the number pad. It's the dash most people are looking for in writing. It is used to indicate a change in thought or tone or to replace sets of parentheses or colons. For example, "Our dinner—which was delicious—had five courses." It can also be used in dialogue to indicate the speaker has been interrupted. For example:

"But you said—"

"I said I'd do it when I'm ready!"

The em dash can be used effectively in writing, but be careful not to overuse it. An overabundance of em dashes can be distracting, and they tend to lose their effectiveness when used too often.