In commerce and industry, 24/7 or 24-7 service (usually pronounced “twenty-four seven”) is service that is available any time and, usually, every day. An alternate orthography for the numerical part includes 24×7 (usually pronounced “twenty-four by seven”). The numerals stand for “24 hours a day, 7 days a week”. Less commonly used, 24/7/52 (adding “52 weeks”) and 24/7/365 service (adding “365 days”) make it clear that service is available every day of the year.
Synonyms include round-the-clock service (with/without hyphens), especially in British English,and nonstop service.
The Oxford English Dictionary (OED) defines the term as “twenty-four hours a day, seven days a week; constantly”. It lists its first reference to 24/7 to be from a 1983 story in the US magazine Sports Illustrated in which Louisiana State University player Jerry Reynolds describes his jump shot in just such a way: 24-7-365.