9/11

American  

[nahyn-i-lev-uhn] / ˈnaɪn ɪˈlɛv ən /

Or 9-11

1. September 11, 2001: the day on which Islamic terrorists, believed to be part of the Al-Qaeda network, hijacked four commercial airplanes and crashed two of them into the World Trade Center in New York City and a third one into the Pentagon in Virginia: the fourth plane crashed into a field in rural Pennsylvania.

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9-11 Cultural  

1. See September 11 attacks.

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Etymology

Origin of 9/11

First recorded in 2000–05

Example Sentences

It was particularly hard-hit on 9/11, with the surrounding Nassau County losing around 350 people, including many first responders.

From BBC • Apr. 10, 2026

In her diary, she notes 1973’s “Tennis Battle of the Sexes” between Billie Jean King and Bobby Riggs, the 1995 Oklahoma City bombing, 9/11 and the advent of Covid-19.

From The Wall Street Journal • Apr. 6, 2026

Giuliani, on the other hand, made national headlines as “America’s mayor” for his leadership during the 9/11 crisis, and immediately became a plausible candidate for president.

From Salon • Apr. 4, 2026

Founded in the wake of the 9/11 attacks and funded by the CIA’s venture-capital arm, Palantir sought to target terrorists and defend American interests.

From MarketWatch • Apr. 4, 2026

He’d assign us reports where we reimagined periods of significant deaths—the plague, the world wars, 9/11, et cetera—and how people would’ve behaved had Death-Cast been around to deliver the warning.

From "They Both Die at the End" by Adam Silvera