- Indicates a sudden break or abrupt change in continuity: “If—if you'll just let me ex-plain—” the student stammered. And the problem—if there really is one—can then be solved.
- Sets apart an explanatory, a defining, or an emphatic phrase: Foods rich in protein—meat, fish, and eggs—should be eaten on a daily basis. More important than winning the election, is governing the nation. That is the test of a political party—the acid, final test.—Adlai E. Stevenson
- Sets apart parenthetical matter: Wolsey, for all his faults—and he had many—was a great statesman, a man of natural dignity with a generous temperament…—Jasper Ridley
- Marks an unfinished sentence: “But if my bus is late—” he began.
- Sets off a summarizing phrase or clause: The vital measure of a newspaper is not its size but its spirit—that is its responsibility to report the news fully, accurately, and fairly.—Arthur H. Sulzberger
- Sets off the name of an author or source, as at the end of a quotation: A poet can survive everything but a misprint.—Oscar Wilde
See also: The Dash and the Hyphen.