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

After 9/11, she worked for the ACLU, representing the Sikh community in a series of discrimination lawsuits.

From Salon • Apr. 12, 2026

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

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

Millennials have 9/11 and the 2008 financial crisis.

From The Wall Street Journal • Mar. 9, 2026

In our country, everyone knows about 9/11 and Osama bin Laden.

From "Malala: The Girl Who Stood Up for Education and Changed the World" by Malala Yousafzai