By Dylan Wiliam

ThinkstockPhotos-99759878There is a long-standing schism amongst people who write dictionaries. Some think dictionaries ought to provide the correct usage of words, while others think dictionaries should reflect how words are used.

For example, the word meld, which used to mean show (as in the card game Bezique) is now used as if it were a combination of melt and weld. This is, of course, how language develops—and I suspect few people will mourn the loss of the original meaning of meld. However, recently, essentially illiterate uses of two words—epicenter and inflection—seem to have reached epidemic proportions.

To a geologist, the epicenter of an earthquake is not the center of the earthquake; it is the point on the earth’s surface closest to the center of the earthquake. Since earthquakes at the earth’s surface are effectively impossible, the epicenter of the earthquake is never the center. So when Thomas Friedman wrote in the New Yorker that the US Department of Education was “the epicenter of national security,” I suspect he was trying to say that the center of national security was at the Department of Education, but he actually said the opposite.

Friedman has also talked a lot about “points of inflection.” A point of inflection in a graph is a point where the graph isn’t flexing—in other words, where the graph is, for an instant at least, straight. A trend has a point of inflection when it stops slowing down, and starts speeding up, or vice-versa. Another way to think about a point of inflection is a point where a cyclist, following the graph, would be vertical, rather than banking either left or right.

It is not the same as a turning point. A turning point is the point where the trend changes direction (from decreasing to increasing, for example). When house prices stop falling and start rising, that’s not a point of inflection—it’s just a turning point. But that probably sounds rather too prosaic…

Have a Question for Me?

I’m ready to answer it! Send me any questions you have about embedding formative assessment, college and career readiness, Common Core State Standards, or any other hot topic in education. In next month’s issue, I’ll offer my thoughts on the subjects that matter most to you.