hyphens and dashes

Modifying phrases are hyphenated when used before a noun, but not after — unless the hyphen is needed to prevent confusion:

  • He was a well-known man.
  • He was well known.
  • She has a full-time job at Brown.
  • She works at Brown full time.

Words formed with prefixes (nonprofit, predate, pre-existing) are only hyphenated to avoid duplicate vowels and consonants.

  • anti-inflation
  • shell-like
  • pre-empt

Two or more hyphenated modifiers having a common base are treated in this way:

  • long- and short-term memory
  • two-, three- and 10-minute intervals

Do not use a hyphen after words ending in “ly” followed by a participle or adjective:

  • poorly attired man
  • historically underrepresented group

Use an em dash (—) sparingly to indicate emphasis or explanation, to define a complementary element or to denote a sudden break in thought. Put a space on each side of an em dash.

  • The influence of three impressionists — Monet, Sisley and Degas — can be seen in his work as a painter.

Note: On an Apple keyboard, form an em dash by selecting option+shift+hypen. On a PC select Alt+0151.