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A conference attendee tries Google Glass during the Google I/O developer conference in San Francisco in May. Justin Sullivan/Getty Images hide caption

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Visitors paid their respects at a makeshift memorial on Boylston Street on April 20, near the scene of the Boston Marathon bombings. Timothy A. Clary/AFP/Getty Images hide caption

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Geoff Nunberg says a good definition extends to the past as well as the present: It's not just about what "marriage" has come to mean; it's all the word has ever meant. hide caption

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Linguist Geoff Nunberg finds that in the film Lincoln, screenwriter Tony Kushner oscillates between old and modern meanings of "equality." DreamWorks/Twentieth Century Fox hide caption

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There are those who say the phrase "the whole nine yards" comes from a joke about a prodigiously well-endowed Scotsman who gets his kilt caught in a door. iStockPhoto hide caption

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Geoff Nunberg says that, like a lot of the Britishisms peppering American speech these days, "spot on" falls somewhere in the blurry region between affectation and flash. Zdenek Ryzner/ hide caption

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President Obama and Republican presidential candidate Mitt Romney finish their debate at the University of Denver on Oct. 3. Saul Loeb/AFP/Getty Images hide caption

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In 1961, the publication of Merriam-Webster's Third International Dictionary sparked an uproar with its inclusion of the word "ain't." Flickr User Greeblie hide caption

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Rep. Paul Ryan has made changes to social safety net programs like Medicare and Social Security — often called "entitlements" — a key part of his political agenda. Win McNamee/Getty Images hide caption

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The word "hopefully" has been used in thousands of NPR stories. Stephanie d'Otreppe/NPR hide caption

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