9/11

an abbreviation for the date September 11 , 2001. It is used to refer to the terrorist attacks that took place on that day in the US and often appears in phrases describing people or things connected with them, e.g. 9/11 families (= families affected by the attacks), the 9/11 Commission , the post-9/11 world . People in the US write dates in the form of the month followed by the day, whereas in Britain the month follows the day. But the US form is used in both countries to refer to the day of the attacks.