Punctuation

In General

Use only one space after end punctuation (periods, exclamation points, question marks) and after colons and semicolons.

Colons

Use colons to introduce a series or a list, especially a list preceded by as follows or the following. Capitalize material after a colon if it constitutes a complete sentence. Use a colon to introduce an explanatory phrase or sentence.

Commas

Between Proper Nouns

Use a comma between two proper nouns (or a year and a proper noun) to aid reading.

  • When he spoke at Crisler Arena, the Dalai Lama attracted a huge crowd.
  • In 2006, President Mary Sue Coleman launched the President’s Donor Challenge.
In Complex and Compound Sentences

Use a comma before a conjunction that introduces an independent clause. Note that you do not need a comma before every and, but, because, and or. If what follows the conjunction is not a complete clause, you don’t need a comma (as in the second example).

  • The orchestra is giving a concert in Hill Auditorium on Friday night, and the Choral Union performs at the Power Center on Saturday night.
  • Parking downtown is a nightmare when the Tigers have a game and there is a concert at the Fox Theatre on the same evening.
With Dates

No comma is needed between a month and a year. Do use a comma before and after the year if month, date, and year are used.

  • The enrollment deadline is December 15, 2007, for residents and December 31, 2007, for non-residents. Classes will begin in February 2008.
Dashes

Observe the distinction between hyphens (-), en dashes (–), and em (—) dashes.

En Dashes

Use en dashes between inclusive numbers and with compound adjectives when one element consists of more than one word.

  • The quiz will cover pages 153–66 of your textbook.
  • The Ann Arbor–Chicago train takes about five hours to reach its destination.
Em Dashes

Use em dashes to indicate a sudden break in thought or an abrupt change in sentence structure. With few exceptions (e.g., in display typography, such as headlines), set dashes without a space on either side.

  • Professor O’Connor—who had won the Nobel Prize in physics the previous year—submitted her resignation to the department chair that morning.

Ellipses

Use ellipses to indicate that material has been omitted from the middle of a quotation. Do not use ellipses at the beginning or end of a quotation even if you start or stop in the middle of the quoted sentence. Create ellipses with three period characters, separated by a single space on either side of each character: . . . not ...