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

Most believed, wrongly, that Hussein had aided in the 9/11 attacks.

From Slate • Mar. 11, 2026

In the years after 9/11, Oceanside was covered in yellow ribbons meant to support the troops.

From Los Angeles Times • Mar. 9, 2026

The position of DNI was created to fix major structural failures in how U.S. intelligence agencies coordinated before 9/11.

From Salon • Mar. 5, 2026

Stocks behaved similarly after 9/11 — although that happened to coincide with a deflating technology bubble.

From MarketWatch • Mar. 3, 2026

Certainly after 9/11 it was more fraught than before, and then it had calmed for a few years.

From "Zeitoun" by Dave Eggers