In typography, three basic characters used either for hypenation, to set off parenthetical text, or express a numerical range. The smallest dash is the hypen (-), used for breaking words or syllables at the ends of lines, or for compound or connected words (such as "mother-in-law"). The en dash (–) is used to replace the words to or through (as in "pages 1–9"). It is also used to connect two nouns of equal weight (as in "East–West alliance") or to replace a colon. If an en dash is unavailable, two hyphens may be kerned together. En dashes are always set closed. An em dash (—) is the largest dash available, and is used to indicate missing material (as in "Dr.— was the murderer"), for parenthetical remarks requiring special emphasis or indicative of a break in thought (as in "Good God—he shrieked in horror—what is that thing?"), or to replace a colon (as in "Here's the diagnosis—"). Em dashes may be set closed or open, open-set dashes providing more opportunities for end-of-line breaks, although modern typesetting equipment will break an em dash if it occurs at the end of a line.
Generally, dashes should not be carried over to the beginning of the following line, if it can be avoided. In some cases, an intermediate dash between an en and em (called a 3/4 em dash) is available, and is used in narrow typefaces or condensed type in lieu of an em dash, as a means of reflecting the narrow feeling of the type design.