7 or 24

In commerce and industry, 24/7 or 24-7 service (usually pronounced "twenty-four seven") is service that is available at 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, but the latter can also refer to other things, such as public transport services which go between two stations without stopping.
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.

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