The Dash

Take a look at the sentence with dashes below.

Standard

Dashes are—and I wish to emphasize this—not hyphens.

Whereas a hyphen connects two words, a dash sets off nonrestrictive groups of words for emphasis. Remember that nonrestrictive phrases can be removed from a sentence without changing the essential meaning of the sentence.

Standard

Shakespeare arrived in London—a town of moderate sophistication—in the late 1580s or early 1590s.

I just finished reading a book you'd enjoy—A Place to Hang the Moon.

A dash is longer than a hyphen—it is composed of two hyphens or a long dash. Do not put a space before or after a dash.