Dash It All

Hyphens, and Em-dashes, and En-dashes, Oh My!

Hyphens and dashes are common pieces of punctuations that can really improve your writing—if you know how to use them. Hyphens can show relationship between words and numbers. Em-dashes can lend your writing a bit of excitement. And en-dashes can show a range in an elegant manner. Today, a brief rundown of what they are and how to use them.

The Hyphen (-)

It's just a little horizontal line, but the hyphen is a handy piece of punctuation. Among its many uses:

• To join two words in a compound word, such as a phrasal adjective:  brand-new blogger
  
• To join two names in a compound name: Robert Smith-Jones
• To show word divisions: tan-ta-lize
• To separate characters: 555-123-4567
• In e-mail addresses and URLs

Note, however, that adverbs that end in -ly are not hyphenated in an adjective phrase as a rule: lovingly made mittens. I notice this a lot from writers who use AP Style, and it drives me crazy. Did AP once say to use a hyphen with a phrasal adjective containing an -ly adverb? (Honestly, I don't know. If you do, tell me!) And because I've said this is the rule, I'm sure someone will come up with an exception to it. If so, please leave it in the comments below.

Did you notice another use of the hyphen? It can be used to show prefixes and suffixes, as in -ly.

The Em-Dash (—)

The em-dash is so called because it is the width of the capital m in the same font. Often on the Web (and back in the day, on a typewriter), it is represented by two hyphens (--), though you can use one of the ASCII codes: ampersand-pound-8212-semi-colon or ampersand-mdash-semi-colon. Some style guides put a space before and after it (e.g., AP Style); some don't have a space on either side of it (e.g., Chicago). Either way, the em-dash's most common use is to set off a part of the sentence, usually with strong emphasis. You could also use a comma, a colon, or parentheses to set off the text, but be sure to match the punctuation's strength with your words' emphasis.

Don't forget if you set off a word or phrase in the middle of the sentence, you need a matching set of punctuation marks. That is, if you introduce a phrase with an em-dash, you must also end the phrase with an em-dash. Same applies if you go with a less-emphatic punctuation mark.

Grammar Girl has a helpful post on em-dashes versus colons. This has stayed with me:

A dash also introduces extra material, but, well, a dash is quite a dramatic punctuation mark. A dashing young man is certainly not an ordinary young man, and if you're dashing off to the store, you're not just going to the store, you're going in a flurry.

The En-Dash (–)

The en-dash is half the width of an em-dash (ASCII codes: ampersand-pound-8211-semi-colon and ampersand-ndash-semi-colon). I see fewer and fewer en-dashes in everyday copy; it seems to be relegated to very formal writing only. Which is too bad, because the en-dash is a useful little piece of punctuation:

• It can represent the word to in a range: 2001–2009. Used this way, both ends of the ranges are included, which is a fine point often ignored these days. And with the en-dash, you don't need the from to precede your range: The Christmas sale, running Saturday–Monday, will offer great savings.
• It can join a phrasal adjective when part of phrase is an open compound: New Mexico–based.
• It can represent a range with no ending: 2001–.
  

Further Reading

These resources offer deeper discussions into hyphens and dashes, as well as explain a couple other, rarer dashes (so rare that I've never used them).

• Words into Type
  
• Garner's Modern American Usage
  
• The Chicago Manual of Style