Punctuation, for many — many — writers, represents a reprehensible beast, a monster with which grade school teachers tortured us, an entity of pure enmity — a featureless creature of ambiguous utility. Why do we need to learn this — asked we — Can't people still understand it without that comma?
If this is you, then behold: the em dash — the great weapon of Emily Dickinson's (right) affection, the very needle-tool of James Joyce's yarn spool!
Em dashes — which are the width of the letter 'm' and not found on your keyboard — "are used to set off or emphasize the content enclosed within dashes or the content that follows a dash," according to Purdue's excellent OWL site. In this definition, note carefully the uncertain term "to set off." This definition rightly implies that the dash — our mysterious friend — is capable of many things:
