Hyphens and dashes are another tricky punctuation pair. A hyphen is a short horizontal line (next to a zero on a keyboard); a dash is longer. But the differences between them go much deeper than just a few fractions of an inch.

The most common use of the hyphen is to divide words at the ends of lines. The important rule to remember is that you may divide words only between syllables. Why is this important, you ask? Read the following lines:

See how difficult this is to read? That's because you've learned to read in syllables. When words aren't divided correctly, readers have to go back to the previous line and put the syllables together, and that's confusing and time-consuming.

The text should read:

If you're not sure where syllables occur, consult a dictionary. In addition, most word processing software contains automatic hyphenation tools you may use. Since you may divide a word only between its syllables, one-syllable words may not be divided.

No matter where the words are divided, be careful to leave more than one letter at the end of a line (or more than two at the beginning of a line) so that readers' eyes can adjust quickly.

You wouldn't write:

Nor would you write:

You should also avoid hyphenating acronyms (such as UNESCO or NAACP), numerals (such as 1,200 or 692), and contractions (such as haven't, didn't, couldn't). Also, some style guides say that proper nouns (those that are capitalized) shouldn't be hyphenated.

Also try to avoid dividing an Internet or e-mail address. Since these addresses often contain hyphens as part of the address, inserting an extra hyphen would certainly confuse readers. If angle brackets aren't used (see Chapter 5), extending the address to the second line without any extra punctuation would make the address clear for your reader. You should do that this way:

Hyphens with Numbers

Use a hyphen (not a dash) between two dates and between two page numbers:

Technically, both of these instances use what's called an “en dash,” which is longer than a hyphen and shorter than a normal dash, which is usually called an “em dash.” Are you confused? Don't be. Most word processing programs have an INSERT icon or a character map that you can use to access en and em dashes, as well as other symbols.

Another common use of the hyphen comes when numbers are written as words instead of numerals. You probably do this already, but the rule says to hyphenate numbers from twenty-one to ninety-nine. If you look at words printed without a hyphen (e.g., sixtyfour, eightyseven), you see that they're difficult to read. Using hyphens makes reading easier.

Hyphens with Compound Adjectives

When a compound adjective (two or more adjectives that go together to form one thought or image) precedes the noun it modifies, it should be hyphenated. Look at these sentences:

In this case, nineteenth-century is an adjective (it modifies the noun writer), and so it's hyphenated. Notice the difference:

Here, nineteenth century is a noun, so it's not hyphenated.

Use a hyphen to join adjectives only if together they form the image. If they're separate words describing a noun (as big, bulky package), then don't use a hyphen. Take a look at this example:

Long and time go together to form the image that describes the friend, so they're hyphenated. If the hyphen weren't there, then readers would see long time friend and would wonder what a long friend was or what a time friend was.