DENNIS BARON is a professor of English and linguistics at the University of Illinois at Urbana-Champaign. His essays and commentaries on language issues have appeared in newspapers and scholarly journals as well as on CNN, NPR, the Voice of America, and the BBC. He tweets @DrGrammar. This piece was first delivered as a lecture with an accompanying slide presentation; this version was published on Baron’s blog, Web of Language, in 2010.