Protesters in San Francisco block a Google bus, which shuttles employees from the city to its location in Silicon Valley. cjmartin/Flickr hide caption

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Decades ago, the SAT test was seen as a measure of raw ability, not as something students ought to cram for. Now, test prep is a huge industry. Linguist Geoff Nunberg wonders what exactly students learn when they're flipping through vocabulary flashcards. Mario Tama/Getty Images hide caption

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President Obama and British Prime Minister David Cameron pose for a "selfie" with Danish Prime Minister Helle Thorning Schmidt during the memorial service for Nelson Mandela. Roberto Schmidt/AFP/Getty Images hide caption

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Sen. Rand Paul, R-Ky., talks to reporters at the U.S. Capitol on Sept. 3. Chip Somodevilla/Getty Images hide caption

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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. iStockphoto.com 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/iStockphoto.com hide caption

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