An em dash (—) is mainly used to show a pause in thought. This is helpful when a writer wants to show an abrupt change in thought, but feels that a comma is too weak and a period is too strong. The em dash got its name because it is the length of one em. If you are using Microsoft Word, there are several ways to insert an em dash in your text. You can either let Word do it for you automatically, or insert one manually.
Allow Microsoft Word to automatically insert an em dash while you type. To do this, start typing the sentence and insert two hyphens where you want an em dash, but make sure to connect the hyphens to the words before and after the em dash. If you space between the words and the hyphens, it will appear as two hyphens (--) and not an em dash (—).
Place an em dash in your Word document by using a keyboard shortcut. Place the cursor exactly where you want to add the em dash. Press the "Num Lock" button on your keyboard to activate the number lock feature on your numeric keypad. Hold down the "Alt" button and type in 0151 with the numeric keypad. The em dash will appear as soon as you type that key sequence.
Insert an em dash in your Word document by using the "Special Character" feature. Position the cursor in the exact spot that you want the em dash to be, and then click on "Insert" from the menu bar at the top of the page. Select "Symbol," and then click on "More Symbols." Choose the "em dash" option from the "Special Characters" tab.