Hyphen or dash - what's the difference?

A hyphen and a dash are both relatively short horizontal lines. For that reason, writers can be unsure about the difference between the two and confused about whether to use a hyphen or a dash in a particular situation.

• A hyphen is used to join two words to form a compound word.

Our daughter and son-in-law live in North Carolina.

Note: You may see compound words, such as African American, written both with and without hyphens. Such compound words are not hyphenated when used as compound nouns but are hyphenated when used as compound adjectives.

• A hyphen is used in writing compound numbers from twenty-one to ninety-nine.

Helena celebrated her twenty-first birthday by taking a Caribbean cruise.

• A hyphen is used in writing a fraction which is used as an adjective.
  

A change in the by-laws requires a two-thirds majority vote of the membership.

• In handwritten material, a hyphen may be used at the end of a line when the entire word cannot fit on the line. The hyphen is placed at the end of a syllable where the word is divided to indicate that the syllable(s) at the beginning of the next line are part of that word. (This also applied to typewritten material, but with computer word processing programs, writers using computers no longer hyphenate words at the ends of lines.)

Note: No spaces are used before or after a hyphen.

A dash is a longer version of a hyphen. A dash is created by typing a space, two hyphens, and another space. Many word-processing programs automatically combine the two hyphens into a dash. Others (like this one) do not.

• A dash can be used in place of a colon to introduce a list.

The student art show included a wide variety of art forms -- paintings, lithographs, collages, mobiles, and sculptures.

• A dash can be used to indicate a sudden break in thought or an interruption in dialogue.

I think I'd better -- on second thought, maybe not!

"Well," said Darla, "if you would just let me -- "
"No way!" cried her brother.

• A dash or pair of dashes may be used to set off parenthetical information in a sentence. In this case, dashes create a greater break than commas, though not as great as parentheses.

The china horse -- the one Jenny had given me for my birthday -- fell off the shelf during the earthquake.

In brief: Hyphens (no spaces between hyphens and words) are used to join words. Dashes (spaces between dashes and words) are used in various ways that separate parts of sentences (as explained above).