American history was forever altered on September 11, 2001, when thousands of people lost their lives at the hands of terrorists.
But there was a lesser-known change that was also initiated that day — a change to the English language, one that has caught the attention of linguists and shaped the way we talk about terrorist attacks.
The innovation is the simple term "9/11," which Americans use to refer to both the date of the attacks and the attacks themselves.
While the term might not seem very special at first glance, "9/11" — pronounced "nine eleven" — defies the way Americans typically refer to calendar dates. Our independence day is "July Fourth" or the "Fourth of July," but never "seven four."
It also defies how we typically talk about disasters — we remember "Pearl Harbor," but not necessarily "12/7." The reasoning for this is pretty clear: The September 11 attacks took place in multiple locations, so it would be difficult to come up with a single term that encompasses the whole thing.
Linguists were quick to pick up on the unusual construction: The American Dialect Society, a group of linguists and language experts, named "9/11" its 2001 Word of the Year for its widespread popularity. Interestingly, the term caught on worldwide, even in countries where dates are typically written in the day-month format.
In the coming years, a handful of other major terrorist incidents got the calendrical treatment, including the 2005 London bombings ("7/7") and the 2004 Madrid bombings ("11-M," referring to March 11).
Appropriately, as Adrienne LaFrance wrote for Medium in 2013, referring to the September 11 attacks by their date helps Americans keep their collective promise to "never forget" them.
"Using calendrical shorthand to refer to a disaster seems inherently part of this push to remember, because knowing an event by its date is in itself a means of ensuring commemoration," she wrote.
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