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  9/11

  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.
• 9-11
  9-11

  See September 11 attacks.

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

See Examples For:

9/11 9-11

The sentiments of celebrities regarding the attacks of 9/11 will be of interest to many.

From The Wall Street Journal ● Aug. 20, 2026

Cobbled together in the aftermath of 9/11, the agency has 7,100 armed, highly trained agents and another 800 criminal analysts, as well as access to troves of confidential data about hundreds of millions of Americans.

From Salon ● Aug. 15, 2026

Joseph Fransen, the study’s chief author, told the Commission that he took inspiration from the federal government’s 9/11 after-action report, which dissected mistakes leading up to the terrorist attack.

From Los Angeles Times ● Aug. 12, 2026

To quickly recap: In 2019 the streamer said that America “deserved” 9/11, a comment he apologized for shortly afterward and has since disavowed.

From Slate ● Aug. 7, 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

The swap was part of a three-day ceasefire that the two sides had agreed to from 9-11 May, which covered Russia's scaled-down Victory Day parade in Moscow.

From BBC ● May 15, 2026

Unions called the February 9-11 strike, accusing the authorities of ignoring warnings about the safety of infrastructure and failing to invest enough in the network.

From Barron's ● Feb. 9, 2026

Sam, in year six, says he thinks we should have longer holidays "because, in countries like Ireland and Spain, they have 9-11 weeks."

From BBC ● Jul. 19, 2025

After numerous attempts to reach him via phone, the employee called 9-11 asking for a welfare check at his Bass Lake home.

From Los Angeles Times ● Jul. 18, 2025

Washington, George, requests opinions of cabinet on French treaty, 6; issues proclamation of neutrality, 8; Farewell Address, 9-11.

From From Isolation to Leadership, Revised A Review of American Foreign Policy by John Holladay Latane