When to Use—and Not Use—an Em-Dash, by Chris Lele, read by Mignon Fogarty, Grammar Girl’s QuickandDirtyTips.com™
When people think of punctuation marks, it is usually the handy comma, the imperious colon, or the overly excited exclamation mark that comes to mind. The stodgy semicolon and sinuous question mark might get thrown into the mix, but rarely—if ever—will somebody mention a punctuation mark that, while omnipresent, often goes unnoticed. This is surprising considering that this punctuation mark is highly versatile and a favorite of skilled writers. It can add a spice—or a dash, if you will—to a sentence by adding emphasis to certain words and phrases.