Hyphens and Dashes

Hyphen | Dashes | Em Dash | En Dash

Hyphens are used for different reasons than dashes. The following paragraphs explain the distinctions.

Hyphen

Use a hyphen

  • When two- or three-word modifiers precede the noun.

    • high-volume, cost-competitive semiconductor production

  • To reduce confusion or ease the reading of compound words and some prefixes for words.

    re-sign (as opposed to resign), burn-in, P-N junction, non-deposition phase

    NOTE: Most prefixes are no longer hyphenated. A usage table for common prefixes is in The Chicago Manual of Style.

  • To add a prefix to a proper noun.

    • mid-January timeframe

  • To show relationship when the first element or prefix for a compound term must temporarily stand alone.

    one- or two-page description, high- or low-level radiation

Do not use a hyphen

  • When compound modifiers follow the noun.

    • high-volume semiconductor production that is cost competitive

  • When compound modifiers combine an adverb and adjective.

    • highly sensitive material
    optimally focused lens

  • When adjectives are composed of foreign words (unless they are always hyphenated).

    in situ measurement
    a priori argument

Dashes

There are two basic types of dash: an em dash (—) and an en dash (–). When using dashes, keep in mind

  • Dashes are not surrounded by spaces.
  • The first word after a dash within a sentence is not capitalized unless it is a proper noun.

Em Dash

Use an em dash to

  • Set off an explanatory or appositive series

    • The company has established a worldwide customer base in all major markets—the U.S., Europe, Japan, Korea, and Taiwan.

  • Set off parenthetical elements more sharply and emphatically

    • The 1990 plan—both the planning process and the finished product—attests to the increasing level of maturity and effectiveness at SEMATECH.

  • Set off a phrase that typically requires commas, but one in which using commas would cause confusion

    Knowledge from the SEMATECH member companies, America's equipment and material suppliers (SEMI/SEMATECH), and the Department of Defense (DOD) are brought into SEMATECH—along with information from American universities, research institutions, government laboratories and agencies, and the Semiconductor Research Corporation (SRC).

En Dash

Use an en dash to

  • indicate a range

    May–June

    pp. 21–34

 
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