For other uses, see Fortnight (disambiguation).
Look up fortnight in Wiktionary, the free dictionary.

A fortnight is a unit of time equal to 14 days (2 weeks). The word derives from the Old English: fēowertyne niht, meaning "fourteen nights".[1][2]

Fortnight and fortnightly are commonly used words in the English-speaking world. Some wages, salaries, and social security benefits are paid on a fortnightly basis;[3] however in North America it is far more common to use the term biweekly. Neither of these terms should be confused with semimonthly, which divides a year into exactly 24 periods (12 months × 2), instead of the 26 (≈52 weeks ÷ 2) of fortnightly/biweekly.[4]


For more information see eclipse cycle.

In astronomy, a fortnight is half a synodic month, the mean time between a full moon and a new moon (and vice versa). This is equal to 14.77 days.[5][6]

In other languages

In many languages, there is no single word for a two-week period, and the equivalent terms "two weeks", "14 days", or "15 days" (counting inclusively) have to be used.

See also


  1. "Fortnight". The Concise Oxford Dictionary (5th ed.). 1964. p. 480.
  2. Senight, sennight or se'night (seven-night), an old word for the week, was still in use in the early 19th century, to judge from Jane Austen's letters.
  3. "Australian Government - How much Disability Support Pension do I get?". Archived from the original on 16 April 2008. Retrieved 22 May 2008.
  4. Steven Bragg (22 June 2010). "What is the difference between a semimonthly and biweekly payroll?". AccountingTools. Retrieved 23 November 2015. Semimonthly is paid 24 times per year, and the biweekly is paid 26 times per year.
  5. Littmann, Mark; Fred Espenak; Ken Willcox (2008). Totality: Eclipses of the Sun. Oxford University Press. ISBN 0-19-953209-5.
  6. Synodic Month definition Eric W. Weisstein
  7. BBC (16 October 2014). "BBC Wales - Catchphrase". BBC Wales. Retrieved 18 November 2016. Wythnos is a week.
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