“Unfriend” is the New Oxford American Dictionary's 2009 word of the year, while “distracted driving” was the pick at Webster’s. Ammon Shea, author of Reading the OED: One Man, One Year, 21,730 Pages (Perigree, 2008) and Mike Agnes, editor in chief of Webster’s New World College Dictionary, explain what goes into the selections.

Contest: Check out the list of the guests’ words-of-the-decade and see how many you can use in a sentence to be read on the air.