24/7 ( to mean round the clock)

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Senior Member
Hello, Dear natives,
I would like to know if the underlined bit is correct.
During inspection, this service is fully available 24/7.
Do I need to add: h/ hour/ day to mean round the clock?
Thank you.
  • mplsray

    Senior Member
    Thank you mplsray for your quick response.
    Is this also right in correspondence?
    I would say that it is the same in informal correspondence, but if you are writing a formal letter, it's probably best to avoid it.

    24/7 (or 24-7 or twenty-four seven) is given the label "slang" here in a couple of dictionaries at Dictionary.com: Dictionary.com Unabridged, based on the Random House Dictionary, and The American Heritage Dictionary of the English Language, 4th ed. The Oxford English Dictionary, which has an entry for 24-7, but shows the other two spellings as well, labels it "colloq. (orig. and chiefly U.S.)."

    Google Books shows examples of twenty-four hours a day, seven days a week; 24 hours a day, seven days a week; and 24 hours a day, 7 days a week. If I were to use it in a formal letter, I think I'd choose the version which spells out the numbers.

    It also shows examples of 24/7, of course, but I would still suggest avoiding it in formal correspondence.
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