When the 9-1-1 system was originally introduced, it was advertised as the "nine-eleven" service. The advertising was changed when concerns were expressed that some types of callers, most notably smaller children, tend to be very literal, and might waste emergency response time trying to find a non-existent "eleven" key on their telephones. Therefore, all references to the telephone number 9-1-1 are now always made as "nine-one-one", and never as "nine-eleven", according to standards outlined by the National Emergency Number Association (NENA). Some newspapers and other media require that references to the phone number be formatted as 9-1-1, also a suggested standard by NENA.
- 9-9-9 / nine-nine-nine / nine nine nine / 999 (UK, Irish)
- 1-1-9 / one-one-nine / one one nine / 119 (Maldives, Sri Lanka)
9-1-1 (plural 9-1-1s)
- by extension, an emergency phone call
- by genericization, an emergency