Did You Know?
DASHES AND HYPHENS
The dash is different from the hyphen (-), which is a short line used to join words together, with no space between the words and the hyphen. The dash is a slightly longer line used to signal abrupt changes in the direction of thought in books, newspapers and magazines. For everyday purposes, the keyboard hyphen serves as a dash so long as a space is inserted before and after it - although you may find that automatic formatting functions will make a hyphen into a longer dash when it is keyed in with space on either side.
There are actually two dash styles: the en-dash (–) and the em-dash (—). We could write those as the 'n' dash and the 'm' dash because each describes the width of the dash used. The en-dash is the width of the letter 'n' and the em-dash is the width of the letter 'm'.
Different publishers use different dashes; it is a stylistic choice. The longer em-dash is normally used without space either end. The en-dash, which is more commonly used by students, needs space either end so it is not confused with a hyphen. If you wish to be more precise in the use of dashes, search for 'em dash' in your word-processing program's Help menu - or google em-dash.