911

Chosen by the United States in the 1960s in place of the older British 999 number as a better way to avoid accidental calls from push-button telephones. It is officially pronounced "nine-one-one" and not "nine-eleven;" the latter refers to the September 11, 2001 attacks in New York and Washington, but the pronunciation "nine-one-one" for the phone number was universal even prior to the attacks. 9/11 is universally distinguished from 911 to refer the September 11 attacks. Officially written as 9-1-1 in regulations and materials from the United States National Emergency Number Association and Federal Communications Commission, which is also advocated by some media style guides.