English can be hard for other language speakers to learn. To use just one example, there are at least eight different ways of expressing events in the future, and conditional tenses are another matter entirely. For evidence of the many nuances and inconsistencies of the English tongue, look no further than this tricky poem penned in 1920. (For a sample: “Hiccough has the sound of cup. My advice is to give up!”)

As author Simon Winchester wrote for The New York Times, there’s one English word in particular that’s deceptively simple: run. As a verb, it boasts a record-setting 645 definitions. Peter Gilliver, a lexicographer and associate editor of the Oxford English Dictionary, spent nine months sussing out its many shades of meaning.

“You might think this word simply means ‘to go with quick steps on alternate feet, never having both or (in the case of many animals) all feet on the ground at the same time,’” Winchester writes. “But no such luck: that is merely sense I.1a, and there are miles to go before the reader of this particular entry may sleep.”

This wasn’t always the case, though. When the first edition of the Oxford English Dictionary was published in 1928, the word with the most definitions was set. However, the word put later outpaced it, and run eventually overtook them both as the English language's most complex word. Winchester thinks this evolution is partly due to advancements in technology (for instance, “a train runs on tracks” and “an iPad runs apps”).

He believes the widespread use of run—and its intricate web of meanings—is also a reflection of our times. “It is a feature of our more sort of energetic and frantic times that set and put seem, in a peculiar way, sort of rather stodgy, rather conservative,” Gilliver told NPR in an interview.

So the next time you tell your boss you "want to run an idea" by them, know that you’re unconsciously expressing your enthusiasm—as well as all the other subtleties wrapped up in run that previous words like set failed to capture.

[h/t The New York Times]